What is the Gospel of the Kingdom according to this lesson?

Les explains that this is what is called the Gospel of the Kingdom: Christ was the King of Israel, and He was ready to give them the Kingdom, but they had to repent and be water baptized in order to be ready for that Kingdom. In that setting, Ananias was one of these believers, and Saul was coming after him and others like him. Paul later rehearsed how he had thought he ought to do many things contrary to the name of Jesus of Nazareth, and he acknowledged that he had done such things in Jerusalem against many of the saints, the Jewish believers.