Ga 1:6-8 ¶ I marvel that ye are so soon removed from him that called you into the grace of Christ unto another gospel:
7 Which is not another; but there be some that trouble you, and would pervert the gospel of Christ.
8 But though we, or an angel from heaven, preach any other gospel unto you than that which we have preached unto you, let him be accursed.
There is a doctrine in certain areas of Christianity that claims there was and is a gospel for the Jewish ecclesia and a different gospel for the Gentile ecclesia. Based largely on the following verse.
Galatians 2:7 KJVS
 But contrariwise, when they saw that the gospel of the uncircumcision was committed unto me, as the gospel of the circumcision was unto Peter;
If you look in a Greek Interlinear you will find the word gospel does not appear a second time in Gal 2:7. http://www.scripture4all.org/OnlineInterlinear/NTpdf/gal2.pdf Paul makes it clear to the Galatian church that the gospel that certain Jews came to teach them, was not another gospel but a perverted gospel of grace. If one examines the scriptures you will see there has only been one gospel that was preached to both Jew and Gentile. Peter makes a statement at a council in Jerusalem, which addressed the matter of whether the Gentiles had to observe the law of Moses and be circumcised, which sheds some light on the matter. Peter stated at that time, that the Jewish and Gentile members of the body of Christ, were to both have their hearts purified by faith and Peter further states the Jews will get salvation through the grace of the Lord Jesus in the same way as they. They of course referring to the Gentiles and the yoke of bondage mentioned by Peter in verse 10, was the law of Moses of which man was not strong enough to bear.
Acts 15:7-11 And when there had been much discussion, Peter got up and said to them, My brothers, you have knowledge that some time back it was God’s pleasure that by my mouth the good news might be given to the Gentiles so that they might have faith.
8 And God, the searcher of hearts, was a witness to them, giving them the Holy Spirit even as he did to us;
9 Making no division between them and us, but making clean their hearts by faith.
10 Why then are you testing God, by putting on the neck of the disciples a yoke so hard that not even our fathers or we were strong enough for it?
11 But we have faith that we will get salvation through the grace of the Lord Jesus in the same way as they. Weymouth
Now the last verse bears repeating for a second time for those who think there was two different gospels.
Acts 15:11 But we have faith that we will get salvation through the grace of the Lord Jesus in the same way as they. Weymouth
Apostle Peter mentions two words associated with salvation, faith and grace when he addressed the council, that agrees with Paul’s epistles. One verse of which is known well by most Christians, Eph 2:8&9. He also puts the law in a proper context that agrees with Ro 8:3. You also have to keep in mind that the Apostles were all men off of the street and countryside. Fisherman, tax collectors and men we would today call blue collar workers. They were not highly educated. Apostle Paul came from a somewhat wealthy family and was extensively trained as a Pharisee., Acts 22:3. He would be a better writer and much more familiar with the law of the fathers than the other Apostles. Perhaps that is why God used him to preach and write extensively about the gospel of grace. Another aspect in regards to the church in Jerusalem was that many priests of the law of Moses were converted to Christianity, Acts 6:7. This lead to some cultural dynamics that are not readily apparent during a casual reading of scripture. Although Peter was head of the church and strong in the Spirit, he was very weak in the flesh as many of us are. He denied the Lord three times when under the scrutiny of others, Lk 22:54-62. But that was before he received the baptism of the Holy Ghost. But even after that, Apostle Paul recounts a episode in the book of Galatians where Peter withdrew himself from eating with a group of Gentiles when certain Jews arrived, Gal 2:11-21. It is easily understood how the priests that converted to Christianity had a powerful influence over the church in Jerusalem. The Apostles, as mentioned before, were common men who had spent their entire lives under the guidance and authority of the Levite priesthood. Cultural indoctrination is hard to ignore and often times it is reflex action. Plus God made the Jews that made up Israel of the flesh, Ro 9:6-8, a quarrelsome and contrary people, 1 Thess 2:15, Zec 12:2&3. Granted the Zechariah prophesy applies to the present day but historically this holds true for the religious leader of Paul’s day, as they rebelled against Rome and attempting to establish the Kingdom of God on their own. You have certain verses in the book of Acts that point to the fact that the Apostles acquiesced to pressure placed on them from the Jews in Jerusalem. Most likely the priest who had converted to Christianity, Acts 21:17-24. This incident in the book of Acts is covered by several or more chapters, where ultimately Paul felt the need to appeal the case, which the Jews had brought against him by the Jewish authorities, to Caesar. Since he was a Roman citizen, Act 25:10&11. This incident lead to Paul’s lengthy incarceration in Rome awaiting his case to appear before Caesar. And while in Rome, Jews visited him to hear what he had to say regarding the gospel of salvation. At that point, due to many of them rejecting the gospel message, Paul informed them that the salvation of God went to the Gentiles.
Acts 28:23-28 KJVS
 And when they had appointed him a day, there came many to him into his lodging; to whom he expounded and testified the kingdom of God, persuading them concerning Jesus, both out of the law of Moses, and out of the prophets, from morning till evening.  And some believed the things which were spoken, and some believed not.  And when they agreed not among themselves, they departed, after that Paul had spoken one word, Well spake the Holy Ghost by Esaias the prophet unto our fathers,  Saying, Go unto this people, and say, Hearing ye shall hear, and shall not understand; and seeing ye shall see, and not perceive:  For the heart of this people is waxed gross, and their ears are dull of hearing, and their eyes have they closed; lest they should see with their eyes, and hear with their ears, and understand with their heart, and should be converted, and I should heal them.  Be it known therefore unto you, that the salvation of God is sent unto the Gentiles, and that they will hear it.
You have to keep in mind that God intended for salvation to pass from the Jew to the Gentile to provoke the Jews to jealousy, Ro 11:11. Keep also in mind that the Pharisees and Scribes were well aware of Old Testament prophecy pointing to salvation going from Jew to Gentile. That would be quite a bitter pill for them to swallow. So much so that they fought against this change, 1 Th 2:16, even the priests that converted to Christianity. God writes the pages of history and knows all too well the difficulty in changing individuals and societies. The law of Moses had and still has a powerful hold on individuals and societies today. Perhaps the hold the law had over Israeli society during the days of the early church, and the eroding effect it was having on the doctrine of salvation by grace, was why God saw it necessary for Rome to destroy the Temple and city of Jerusalem. Apostle Peter as the head of the church endorsed Apostle Paul and his epistles.
2Pe 3:15-16 And account that the longsuffering of our Lord is salvation; even as our beloved brother Paul also according to the wisdom given unto him hath written unto you;
16 As also in all his epistles, speaking in them of these things; in which are some things hard to be understood, which they that are unlearned and unstable wrest, as they do also the other scriptures, unto their own destruction.
Further evidence of there being only one gospel is in the fact that Jesus, by his death, abolished the law of commandments contained in ordinances and made the two, Gentile and Jew, one new man.
Eph 2:13-15 But now in Christ Jesus ye who sometimes were far off are made nigh by the blood of Christ.
14 ¶ For he is our peace, who hath made both one, and hath broken down the middle wall of partition between us;
15 Having abolished in his flesh the enmity, even the law of commandments contained in ordinances; for to make in himself of twain one new man, so making peace;
So how can there be two gospels? The whole gist of Gal 2:7, is that Paul was making it clear that God had appointed him to bring the gospel of grace to the Gentiles, Acts 9:15. Paul was given the task of preaching the gospel of grace to the Gentiles and Peter was to bring the gospel of grace to the Jews, nothing more. I think several aspect that makes the whole two gospel misconception plausible is the mystery of God, and a improper understanding of grace. The mystery of God is Christ in you the hope of glory, Col 1:27. If you do a word study on the word mystery, you will find Paul was given the dispensation to disclose the mystery of God to the church at a specific point in time, and that that revelation filled up the word of God, Ro 16:25, Col 1;25-27.
Ephesians 3:3-6 KJVS
 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,  Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)  Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;  That the Gentiles should be fellowheirs, and of the same body, and partakers of his promise in Christ by the gospel:
Notice the wording in verse 6, fellowheirs, and of the same body. When you understand the significance of the mystery of God, you begin to realize that the gospels and epistles written before Paul received the revelation of the mystery of God, lack the entire gospel message regarding the salvation process. I don’t want to go overly long on this, but if you do a word study on the words mystery and sanctified as pertaining to the body of Christ. These words only appear in that context, after the mystery of God has been disclosed by God to Paul. The first three gospels lack knowledge of the mystery by the authors. The gospel of John was written much later, around 90AD, and contain verses that imply knowledge of the mystery of God spoken by the Lord himself.
John 12:24 KJVS
 Verily, verily, I say unto you, Except a corn of wheat fall into the ground and die, it abideth alone: but if it die, it bringeth forth much fruit.
John 17:17,23 KJVS
 Sanctify them through thy truth: thy word is truth.  I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.
Being sanctified or made perfect, He 10:14, are contingent upon the mystery of God which is Christ in you. Furthermore, God in Christ, and Christ in us, is the essence of the mystery of God. The mystery of God is first mentioned by Paul in Ro 16:25. It is then a simple matter to find a list of when the gospels and epistles were written. You might, as I did, print it up, cut to size and tape it to the inside of the front or rear covers of your bible. The gospels and epistles written before the mystery was disclosed, are not going have verses in them that deal with sanctification of the body of Christ. Because again, sanctification is contingent about Christ in you. I think Peter sums it up nicely in 2Pe 3:16. Which is that, unlearned and unstable men wrestle with the scriptures unto their own destruction. The law of the Spirit of life in Christ Jesus, Ro 8:2, is about the heart. God, by His grace and by His Spirit is teaching us how to love one another, 1Th 4:9. Only by the grace of God teaching us and the washing of regeneration and renewal of the Holy Ghost changing us, can the purification of our hearts be accomplish, Titus 2:11&12, Titus 3:5-7. In short the gospel of grace. The law was incapable of doing this, because the flesh is too weak to observe the law.
Ro 8″1-4 ¶ There is therefore now no condemnation to them which are in Christ Jesus, who walk not after the flesh, but after the Spirit.
2 For the law of the Spirit of life in Christ Jesus hath made me free from the law of sin and death.
3 For what the law could not do, in that it was weak through the flesh, God sending his own Son in the likeness of sinful flesh, and for sin, condemned sin in the flesh:
4 That the righteousness of the law might be fulfilled in us, who walk not after the flesh, but after the Spirit.
There is only one gospel and that is the gospel of grace which saves us, Jew and Gentile alike, through the redemption that is in Christ Jesus, Ro 3:23-24. This graciousness of God, wherein He teaches us, chastises us and disciplines us, in tandem with the washing of regeneration and renewal of the Holy Ghost frequently in our lives, is how we are being saved, Tit 2:11-12, He 12:5-11, Titus 3:5-7. Included in this process is sanctification, which is the death of the flesh, that can only take place by the seed of Christ falling into our flesh, crucifying our flesh, Gal 5:4. The end result is being found in Christ at his coming and claiming our inheritance which God promised to Abraham, and to his seed. And that seed of course is Jesus Christ.
Galatians 3:16,29 KJVS
 Now to Abraham and his seed were the promises made. He saith not, And to seeds, as of many; but as of one, And to thy seed, which is Christ.  And if ye be Christ’s, then are ye Abraham’s seed, and heirs according to the promise.
That is the good news of the gospel of the Kingdom of God. But remember, just as there are vessels of mercy who were ordained for God’s purpose, so to, there are others ordained for a different purpose.
Jude 1:4 For there are certain men crept in unawares, who were before of old ordained to this condemnation, ungodly men, turning the grace of our God into lasciviousness, and denying the only Lord God, and our Lord Jesus Christ.
The biggest problems I see dominating Christianity today is it is two pronged. It is on the one hand influenced too much by the law in many denominations. On the other hand grace and how it functions is misunderstood and many denominations encourages lasciviousness.