Paul's stress in Galatians chapter one is to insist that his is not a man-made gospel, but that it comes directly from God. This is a very modern criticism of Paul. You frequently hear about the historical Jesus who was very different from the theological Paul. Paul, they say, was an intellectual who systematized Christianity - turned it into a misogynist, Pharisaical, organized theology, when what Jesus had wanted was a free and easy relationship with the numinous.
Nothing could be further from the truth. The gospel that I preached, he said, is not something that man made up (v 11). I did not receive it from any man, nor was I taught it.
He received it by revelation from Jesus Christ. Paul's experience was unique. Other Apostles received the gospel directly from Jesus - in their years as disciples or the weeks as friends after the resurrection - but uniquely Paul received his gospel after the Ascension. It was a finishing touch of enormous power. It enabled Paul to rebut the charge of being derivative. The Gospel came direct.
This was an important strategy of God's. We know that the disciples had been given the Great Commission. As Jesus was taken up into heaven they were told that they would be his witnesses in Jerusalem, in all Judea and Samaria, and to the ends of the earth. Perhaps somehow this was not happening. Was there some impediment? Some Devilish activity sowing dissension rather than the seed of the Gospel? Perhaps the believers in Jerusalem were like the elders at William Carey's Northampton church, too concerned about not preaching to those who were not the elect? Whatever the cause there needed to be a fresh impetus and God was able to wield the Devil's sharpest tool, Paul, to use against him. Direct revelation to Paul was the answer. Appoint him apostle to the gentiles. (Later another kick in the pants got them out of their sinecure - Jerusalem was sacked in AD 70.)
A comment on that word 'revelation'. Don't think that you can happen on the Gospel by just thinking. So great is the Gospel that it has to be revealed. What would we know of Jesus except that he had been revealed. Paul tells us that we can recognize a creator from the creation, but the nature of grace, the fact that God is love, the person of Jesus Christ, his work upon the cross - all these must be revealed to us. How important then is Scripture! It is a miracle delivered by the Holy Spirit!
After his road to Damascus experience, Paul did not go up to Jerusalem to consult with the authorities so that his 'i's might be dotted and his 't's crossed. He went immediately to Arabia and later returned to Damascus. What he was doing in Arabia we can only guess at. Rest, prayer and meditation may have all been necessary after such a momentous experience. His return to Damascus we can follow in Acts chapter 9. I take it that his time in Damascus was interrupted by his sojourn in Arabia, which could have meant the hinterlands of what we now call Syria. Back in Damascus he began preaching in the synagogues in such a convincing way that all who heard him were astonished. He provoked opposition among the Jews so that he had to be let out of the city down the walls in a basket, since watch was kept on the city gates for him.
Eventually after three years he did visit Jerusalem, but this was a short private, fortnight visit to get acquainted with Peter and a brief visit with James, the Lord's brother. This was a time for touching base. It was not to obtain an endorsement. No doubt there was a two-way sharing of information. But the reaction was "He who formally persecuted us is now preaching the gospel of the faith which he was trying to destroy." A testimony to the power of God.