I've heard many people say that Paul only ministered to the Gentiles. And this is absolutely not true. I would like to refer you to you to Acts 17:2, Acts 17:17, Acts 18:4, Acts 18:19, and Acts 19:8
Paul was for very knowledgeable of the Scriptures and use them very persuasively. Even though on occasion, he would come up against resistance from the Jewish establishment. We can see from acts 17, at one of Paul's challenges was to convince the Jews the necessity of the crucifixion and resurrection of the Messiah. Of course not all of the Jews believe Paul but some of them did. We even see in acts 9:29, that Paul spoke so boldly that the Jews became offended and tried to murder him. In Acts 8:25-27 we see that Philip and John did not confine their ministry to the Jews. In fact, they preached in many Samaritan villages, and Philip ministered to the Egyptian and baptized him.
What is important is that the apostles took the message of Christ wherever they saw a need for it to be preached. I think many times, we feel that we are called to certain ministry and become too focused on that one element of our Christian walk that we ignore targets of opportunity, as we would say in military. If you run for instance, a jail ministry, or a food ministry and fail to see the needs of those that you work with, or those in your family then you're failing, Christ.
So let's take a lesson from Paul and Philip and be prepared to proclaim the good news any time anywhere the opportunity arises.
Peace
JB