When did God turn from the Jews to the Gentiles in the book of Acts?
The shift occurred well into the book of Acts, when the apostle Paul was called aside and God sent him far hence to the Gentiles. Paul continued going first to the Jews in synagogues, then turned to the Gentiles after they rejected him, as seen by Acts 28.
Les teaches that from Genesis 12, the call of Abram, all the way until well into the book of Acts, God dealt predominantly with Jew only. There were Gentile exceptions such as Jonah at Nineveh, Naaman the Syrian, Rahab, and Ruth the Moabitess. After getting well into Acts, Paul was called aside, and God told him He would send him far hence to the Gentiles. By Acts 28, Paul was imprisoned in Rome, near martyrdom, still writing prison epistles. Though he had been among Gentiles for many years, he went first to the Jew in the synagogue, and when they rejected him, he turned to the Gentiles.