One only has to look at Acts to see the 12 ministered to Jews and in some cases and later to Gentiles. Where Paul, Barnabas, Apollo and others minister to mainly Gentile communities. Yes they went to the lost sheep first and when some came aboard and some rejected moved out to the Gentiles. And again we see below a clear distinction between Jews, Gentiles and even further in this case Corinthians:
Acts 18:
5 When Silas and Timothy had come from Macedonia, Paul was compelled by the Spirit, and testified to the Jews that Jesus is the Christ. 6 But when they opposed him and blasphemed, he shook his garments and said to them, “Your blood be upon your own heads; I am clean. From now on I will go to the Gentiles.” 7 And he departed from there and entered the house of a certain man named Justus, one who worshiped God, whose house was next door to the synagogue. 8 Then Crispus, the ruler of the synagogue, believed on the Lord with all his household. And many of the Corinthians, hearing, believed and were baptized.
Gentile communities?
Nonsense!
Every congregation Paul wrote to was a known Hebrew enclave, even the Talmudic writers acknowledge that.