Paul’s gospel was essentially twofold: Christ died for our sins (Rom 5:8; 1 Co 15:3), so that we can live forever (Rom 6:23; Tit 3:7). Both sacrificial atonement (propitiation, justification, reconciliation, etc) and Jewish eschatology (day of Christ, resurrection of the dead, immortality, etc) were gospel to Paul. Christ “gave himself for our sins to deliver us from the present evil age” (Gal 1:4). Anything else is a “different gospel” (v. 6).