The circumcision question is resolved in a meeting in Jerusalem; Barnabas goes to Cyprus, and Paul goes to Syria and Cilicia, visiting Derbe, Lystra, Phrygia, Galatia, then Pilippi in Macedonia, where he’s imprisoned with Silas, before going to Thessalonica (for only a few weeks), Berea, Athens and Corinth: Acts 15–18:17
Peter was the first to see Gentiles receive the Holy Spirit, so he knew, first hand, that salvation was now on offer for everyone, thanks to the grace of God:
Acts 15:8-11 God knows people’s hearts, and He confirmed that he accepts Gentiles by giving them the Holy Spirit, just as he did to us. He made no distinction between us and them, for He cleansed their hearts through faith. So why are you now challenging God by burdening the Gentile believers with a yoke that neither we nor our ancestors were able to bear? We believe that we are all saved the same way, by the undeserved grace of the Lord Jesus.