It is true that now there is but one gospel and God’s curse is pronounced upon any who would presume to proclaim any other (Gal.1:8,9), but those who suppose that Paul proclaimed the same good news which the twelve before him had proclaimed, should carefully read Galatians 2:1-9.
The twelve had been proclaiming our Lord’s kingdom rights in “the gospel of the kingdom”. With the kingdom having been rejected, however, God raised up Paul to proclaim “the Gospel of the Grace of God” (Acts 20:24). In Galatians 1:11,12, this apostle declares:
“But I certify you, brethren, that the gospel which was preached of me is not after man, for I neither received it of man, neither was I taught it, but by the revelation of Jesus Christ.”
This is only one of many passages in which he declares that he was commissioned to proclaim a special message by the glorified Lord Himself (Eph.3:1-4; Rom. 16:25; etc.).
Now in Galatians 2:2, the apostle states: “I went up by revelation [God sent him] and communicated unto them [the apostles and elders at Jerusalem] that gospel which I preach among the Gentiles….” But was he not merely checking to make sure that he and they were preaching the same good news? No, for he goes on to say: “But [I went] privately to them which were of reputation, lest by any means I should run, or had run, in vain”.
Verses 7 and 9 then go on to tell how “they saw” and “perceived” the grace that had been given to Paul, so that they publicly and officially gave him “the right hands of fellowship”, acknowledging him as the apostle of grace, sent to the world with a message of grace:
“Being justified freely by His grace through the redemption that is in Christ Jesus” (Rom. 3:24). source