Hmmm. something DIFFERENT appears to be happening here. Baptism is NOT part of the gospel Paul is preaching. Water baptism, that is. As it was in Acts 8 and Acts 10, and Acts 1, and Matt. Mark, Luke and John.
Acts is a transitional Book. From Law to Grace. From a Kingdom of Believers to a Body of Believers. From Peter and the 11 to Paul. From water baptism to baptism BY the Holy Spirit INTO the Body of Christ.