Is this the time when God is mainly calling Gentiles rather than Jews?
Yes, this is primarily the time of God calling out Gentiles from the unbelieving world. A Jew can also be saved, but the present emphasis is on gathering Gentiles. Paul's message went to the pagan world, and they responded to the Gospel of the Grace of God.
Les explains that while a Jew can be saved as well as a Gentile, it is primarily God's time of calling out Gentiles from amongst the unbelieving world. Paul's message, as seen in the first two letters to the Corinthians, was to the pagan world. He could come to abject pagan people with nothing but the Gospel of the Grace of God, and they would come out of their paganism and become believers, or Christians. Les also notes that any other message would be a perversion of the Gospel of Christ, which is most explicitly laid out in 1 Corinthians 15:1-4, referred to as the Gospel of the Grace of God, the Gospel of God, My Gospel, and the Gospel according to the revelation of the mysteries.