The first part of this chapter was The Unknown Years 1. Other posts in the series include:
1a. Born at a Time and Place 1
1b. Born at a Time and Place 2
2a. A Change in Life Direction
2b A Change in Life Direction 2
2c A Change in Life Direction 3
Paul says in Galatians 2 that his next trip to Jerusalem was "after fourteen years" (2:1). The most obvious way to take this comment is that Paul believed in Jesus (ca. AD33), then went up to Jerusalem a first time some three years later (AD36), then went up to Jerusalem a second time some fourteen years later (ca. AD50). This is in fact how most scholars in general have reconstructed Paul's chronology, placing his second visit to Jerusalem around AD49. 
And no doubt we would all assume this was the case if it were not for the difficulties this straightforward interpretation causes us when we try to fit it with Acts. Here one will have to decide how precisely historical both Paul and Acts are being at these points and decide for oneself. The tension is two-fold. First, Acts 11:27-30 tells of a trip that Barnabas and Paul made to Jerusalem to take famine relief from Antioch. Our best estimates are that this famine took place around the year AD46, although the relief could have course have been taken earlier.
At this point F. F. Bruce made an ingenious suggestion.  He noted that the word for "after" in Galatians 2:1 can also be translated as "through." So he wondered if "through fourteen years" actually started from Paul's conversion rather than from his last trip. His second trip would then turn out to be around 46-47, during the famine. Further, Paul says in Galatians 2:2 that he went up to Jerusalem because of a revelation. And was it not a prophecy that led to the famine relief in Acts 11?
Mention of the revelation leads to the second tension between Paul and Acts here. Bruce's interpretation fails at this point, for Paul does not go up to Jerusalem in Galatians 2 because of someone else's revelation about a famine. Paul goes up privately because of a revelation God has given specifically to him, and it is about the way he is preaching to the Gentiles, not about a famine.
The topic of Paul's second visit to Jerusalem in Galatians 2 is not a famine but is actually much more similar to the Jerusalem Council in Acts 15. Many scholars think that Galatians 2 and Acts 15 are two different versions of the same basic event. They cover the same basic issue--whether Gentile believers must get circumcised to be saved--with the same basic people. The problem is that the two accounts have a quite different flavor to each other. Paul's visit in Galatians 2 is private, informal, and initiated by Paul. The so called "Council of Jerusalem" in Acts 15 is public, somewhat formal, and initiated by the church at Antioch.
Bruce ingeniously suggested that Galatians 2 was a private visit about the subject Paul made during the "gift trip" to bring famine relief in Acts 11. Then Acts 15 was a more formal visit on the subject a couple years later after Paul and Barnabas went on their "first" missionary journey. Bruce also argued that Galatians was written before the Jersualem Council of Acts 15 as another indication as the conflict over whether Gentiles needed to get circumcised to escape God's judgment.
Everyone will have to draw their own conclusion on such issues. We have found it impossible to get past the "after fourteen years" of Galatians 2. Perhaps Paul was omitting reference to the gift trip of Acts as irrelevant to the topic at hand. And you will have to decide how creative Acts was allowed to be in its re-presentation of the early church.
What is clear is that Paul did have some sort of showdown with other factions in the early church over whether or not, and how, Gentiles might escape God's coming judgment. The understanding Paul eventually came to have was that as long as Gentiles truly had faith in Jesus as their Lord, they were children of God, just as the Jews. Whether informally or formally, Paul seems to have secured a very similar allowance from the leaders of the Jerusalem church, especially Peter and James, Jesus' brother. They might not have put it the same way as Paul, but they affirmed that Gentiles could escape God's wrath without fully converting to Judaism and getting circumcised.
Paul won this concession sometime around the year AD49. He took Titus with him to Jerusalem as an example to show the Jerusalem leaders, an uncircumcised believer (Gal. 2:2-3), and they did not force him to become circumcised. However, the wording suggests that they still thought it preferable--but they did not force him. Paul indicates there were other forces in play. He calls them "false brothers" (Gal. 2:4-5). Acts considers them Christians (Acts 15:5).
But the Jerusalem leadership had its limits. Paul did not fare as well in an incident not long subsequent to the inital allowance. At Antioch, Peter was visiting and was eating with Gentile believers--that is, until James clamped down. Jesus' brother, James, had apparently become the leader of the church in Jerusalem. Even Peter seems to have taken a secondary authority next to him. James seems to convince Peter--and Paul's missionary companion Barnabas--to stop eating with Gentile believers, presumably because they brought the potential threat of uncleanness.
Acts 15 presents a verdict on the Jew-Gentile issue that seems to address this issue as well--the
question of how Jew and Gentile can eat together. Bruce would see the incident at Antioch and the writing of Galatians prior to the Jerusalem Council in Acts 15. Others might suggest that Acts 15 is meant to capture in one story a process that historically actually took a longer amount of time to develop and unfold.  Each will have to make up their own mind.
In either case, the Jerusalem leadership seems to have concluded at some point that if Gentiles would follow certain purity guidelines, then the Jews could eat with them (cf. Acts 15:29). Eating together was of major importance for the early Christians. Jews saw "table fellowship" as a central element in belonging to God's people. You ate with those who were truly your people and in your family.
So Gentiles would need to stay away from food that had come from a pagan temple and been sacrificed initially to another god. Much of the meat in any ancient marketplace would have come from such nearby temples. Only the fat was burned up in the sacrifice. Gentiles would need to kill the animals used for food by slitting the throat and draining the blood. Blood could not be a part of the meal in any way. Finally, the Gentiles themselves would need to abstain from sexual immorality, which would make them contagiously impure.
Paul agreed with the part about sexual immorality (cf. 1 Cor. 5:11). But he took a "don't ask; don't tell" approach to matters of food. "I am convinced, being fully persuaded in the Lord Jesus, that nothing is unclean in itself. But if anyone regards something as unclean, then for that person it is unclean." (Rom. 14:14, TNIV). It is thus no surprise that he never endorses the position of the Jerusalem church in any of his writings, even when he is dealing with these issues.
Paul seems to have lost the argument at Antioch over table fellowship between Jew and Gentile. Bruce would like to see the Jerusalem Council solving all these issues and everyone going on in harmony. Indeed, Acts does not even mention this particular conflict, a fact that may indicate a general tendency on its part to minimize early Christian disagreements. It seems little coincidence that Paul and Barnabas have a falling out about this time, even though Acts tells us it focused on whether to take a young man named John Mark on a missionary journey (Acts 15:36-40).
They go their separate ways. And Paul never mentions that he won the day in the Antioch argument, as he does in relation to his visit to Jerusalem and as we would expect him to do, given his personality. The best explanation is that he probably did not convince the leadership of his position. Paul thus embarks on his "second" missionary journey with Silas, at odds with the Jerusalem church. Although Acts gives a strangely passing mention of a quick visit to Jerusalem in the mid-50s (Acts 18:22), Paul would not make a substantial visit to Jerusalem again until the time when he will be arrested. 
In the time between the famine in Jerusalem (ca. AD46) and the Jerusalem Council (ca. AD49), Acts tells of what we conventionally call Paul's "first" missionary journey. This journey started from Antioch with Paul, Barnabas, and the young man we have mentioned above named John Mark. Barnabas and John Mark were apparently cousins (cf. Col. 4:10). The journey starts with the island of Cyprus, which Acts tells us is where Barnabas is from. Acts also gives us the impression that Barnabas was the leader of the missionary expedition.
After they have finished preaching the gospel on Cyprus, they head for the mainland of Asia Minor, just to the north of the island in what is modern day Turkey. Perhaps this region was not part of the original plan. For whatever reason, John Mark abandons the group once they reach Pamphylia, as the southern region of Turkey was called at the time. He returns to Jerusalem. Here is the central reason Acts gives for Paul and Barnabas' later split up. Paul did not consider John Mark reliable as a traveling companion. Perhaps his primary role was to carry things and help with the more mundane parts of the journey.
The mountains are high as you go north. Paul seems to be increasingly exploring the possibility of bringing the gospel to the Gentiles. Perhaps he is increasingly taking charge. Perhaps Paul had a way of getting into trouble with local authorities--they at least had an audience with the Roman governor of Cyprus, although that encounter turned out well. All these reasons may have factored into John Mark's decision.
The rest of the trip involved the southern part of the Roman region known as Galatia. They visited towns like Antioch in Pisidia, Iconium, Lystra, and Derbe. Paul was stoned and left for dead at Lystra, but miraculously survives largely unscathed. Perhaps even most scholars believe that this collection of cities and villages was the target audience of the New Testament book of Galatians. We have fallen off the log with a different conclusion, that it was the area north of these cities that Paul addressed. But we will acknowledge that it is a strong argument. Acts tells us of Paul founding churches in this southern part of Galatia. We have only hints that he later founded churches in the north.
And thus some sixteen or seventeen years after Paul believed on Christ, he and a man named Silas embark from Antioch on what is conventionally known as his "second" missionary journey. In truth, he has been on a mission since he turned to Christ. He went on a mission to Arabia. He no doubt evangelized his home region of Cilicia for years. Then he went with Barnabas to south Galatia. By the time he embarked toward Greece, he had been proclaiming the gospel for almost twenty years...
 The classic work on the chronology of Paul is Paul Jewett's, A Chronology of Paul's Life (Minneapolis: Fortress, 1979), although his reconstruction does have some idiosyncrasies. Another work on the subject, also with idiosyncrasies, is Gerd Ludemann, Paul: Apostle to the Gentiles: Studies in Chronology (London: SCM, 1984).
One of the difficulties is that ancients seem to have counted parts of years as years in such reckonings, as well as the fact that such numbers may at times be very approximate. So "three years" could be more like "two and a bit," and "fourteen" years could be more like "thirteen and a bit" or even less (or more, perhaps).
 Paul: Apostle of the Heart Set Free (Grand Rapids: Eerdmans, 2000 ), is the best place to access Bruce's reconstruction. Although we differ with Bruce at many points, his book is an excellent place to begin the study of Paul and so deserves an early slot among the fifty books and resources you might read to master Paul and his writings.
 Note, for example, that Paul never mentions the letter of Acts 15, even though it was highly pertinent to some of the issues he faced in his churches. 1 Corinthians 8-10 addresses food offered to idols, a key item in the letter. On the other hand, Paul's omission may simply come from the fact that he disagreed with the letter, which is quite likely.
 Jerusalem is not even mentioned explicitly. He lands at Caesarea and goes up and visits "the church" before returning to Antioch and going again through Galatia and Phrygia.