What is the difference between the kingdom and grace gospels?

The kingdom gospel to the Jews is to believe in and confess Jesus as their Messiah and then to do works to prove their faith in their confession. The works to do are to repent and be baptized for the remission of their sin, so that they can receive the Holy Spirit, Act.2:38-39. That is their gospel. In addition to this they were expected to continue faithfully in the Mosaic law, to sell all their possessions and live in common with each other in the church, and endure to the end until their salvation comes at the return of Christ.

The grace gospel to all nations is to hear and believe in the cross work of Jesus Christ; that Jesus, as God’s Son, completely righteous and perfect, died in our place as a willing offering, so that God could impute His righteousness on us and justify us by the price of that sacrifice. There are no works to perform to qualify faith because Jesus did all the work necessary to justify us, and we are not saved by our own faith, but by the faith of Christ Himself, Rom.3:22; Gal.2:16; Phil.3:9. Through Jesus, we are forgiven and can be translated from death to life, being regenerated in spirit, and come to an understanding of God’s will and ways, growing up in Him towards adopted sonship. A summary of Paul’s grace gospel is found in 1Cor.15:1-4.