Paul was not confused about the instruction God gave him to preach the gospel to the gentiles (Acts 26:17-20), but he used the strategy of starting where he was. He started preaching in Damascus where he traveled to when the call came, later on, in Jerusalem his real base, then to Judea and then to the gentiles, the focus of his assignment.
Paul was strategic in his approach to fulfilling his assignment. He was highly knowledgeable, received a lot of revelations directly from God but also very humble and wise in dealing with everyone especially the Jews; so that he would not labour in vain. The Jews did not just want to disrupt his assignment, they wanted to kill him. Therefore, he needed to be very wise. No wonder he said, he behaved like a Jew to the Jew and like a Roman to the Romans.
He kept on preaching among the Jews in his environment and became known as a preacher and teacher until it was time to go to the gentiles. The Holy Spirit Himself communicated with the prophets and teachers to separate him unto the assignments set for him. Notice that he did not forcefully open the door or quarreled with the earlier Apostles to achieve his goal.
Start from where you are. Preach to or teach people in your family, village, community, town, city, etc. before you have the opportunity to go international. Even if nobody recognizes what you are doing, God is recording them. Be wise and humble in dealing with everyone even if you are more knowledgeable. God himself will open up the opportunity for you to reach the actual destination and thereby fulfill your destiny.
Use whatever opportunity you have now, don’t despise your current door waiting for the bigger one.