What does Paul mean when he calls it 'my gospel'?
Paul means the gospel of grace, the gospel of Christ, and the gospel of God—the message committed to him for virgin territory, distinct from the gospel of the Kingdom that Jesus and the Twelve proclaimed to Israel. He was not an extension of the Twelve or building on their labors.
Les explains that much of Christendom preaches the gospel of the Kingdom rather than the gospel of Christ, so people are not hearing the gospel of grace, the gospel of Christ, and the gospel of God—what Paul calls "my gospel." The Kingdom gospel was proclaimed by Jesus and the Twelve to the nation of Israel. Paul, however, says he is not boasting beyond his measure or of other men's labors, and he is not an extension of what the Twelve accomplished or building on what they did. He is in virgin territory because the Twelve's ministry was confined to Israel within its borders. Thus Paul's "my gospel" is the distinct gospel of grace, Christ, and God connected with his own apostolic ministry, not the Kingdom message to Israel.