Now I am speaking to you Gentiles. Inasmuch then as I am an apostle to the Gentiles, I magnify my ministry  in order somehow to make my fellow Jews jealous, and thus save some of them. (ESV)
Paul recognized that God had called him to be an apostle to the Gentiles. In so doing, he had not forgotten about his Jewish brothers and sisters. In the early parts of his ministry when he would come into a city he would always preach to the Jews first, then to the Gentiles. His heart was to reach his own first, and also to reach the Gentiles.
This is a good pattern for us to follow as believers. We should all be passionate about sharing the Gospel with all people. First and foremost we need to share the Gospel with those who are closest to us. Our family members should be the first ones to hear the Gospel from us. In addition to reaching our families, loved ones, and those close by, we also need to spread the Gospel around the world.
Paul's ministry was magnified. In other words it had expanded from just reaching the Jewish people. He recognized that even though most of his converts were from the Gentile people there was an added bonus. The Jews were likely to see all of the blessings that the Gentiles were receiving by coming to Christ. Perhaps they would be jealous and desire to have what the Gentiles had.
This is also another great example for us. We should be living such a changed life by God's grace that the world around us should be jealous of what we have. The most effective witness is not a Gospel tract, or even a sermon. The best witness for the Lord is a changed life. People may dispute the things you say, or even what the Bible says, but they cannot dispute a changed life that they can see.
Who is God calling you to share the Gospel with? Start with your own family. Then ask the Lord to show you who else he would have you to share with. Remember to live a life that people cannot dispute.