Paul's first order during Acts was to preach the gospel of God.
Acts 9:20 And straightway he preached Christ in the synagogues, that he is the Son of God.
Acts 9:21 But all that heard him were amazed, and said; Is not this he that destroyed them which called on this name in Jerusalem, and came hither for that intent, that he might bring them bound unto the chief priests?
Acts 9:22 But Saul increased the more in strength, and confounded the Jews which dwelt at Damascus, proving that this is very Christ.
It was his manner. See more:
Acts 17:1 Now when they had passed through Amphipolis and Apollonia, they came to Thessalonica, where was a synagogue of the Jews:
Acts 17:2 And Paul, as his manner was, went in unto them, and three sabbath days reasoned with them out of the scriptures,
Acts 17:3 Opening and alleging, that Christ must needs have suffered, and risen again from the dead; and that this Jesus, whom I preach unto you, is Christ.
1 Thessalonians 2:2 But even after that we had suffered before, and were shamefully entreated, as ye know, at Philippi, we were bold in our God to speak unto you the gospel of God with much contention.
1 Thessalonians 2:7 But we were gentle among you, even as a nurse cherisheth her children:
1 Thessalonians 2:8 So being affectionately desirous of you, we were willing to have imparted unto you, not the gospel of God only, but also our own souls, because ye were dear unto us.
1 Thessalonians 2:9 For ye remember, brethren, our labour and travail: for labouring night and day, because we would not be chargeable unto any of you, we preached unto you the gospel of God.
And though the dispensation of the gospel was committed unto Paul (1 Corinthians 9:17 KJV) it wasn't necessarily Paul (he was hindered 1 Thessalonians 2:18 KJV), but at times fellowlabourers in the gospel of Christ that would be sent back to establish the believer into the Body. Notice:
1 Thessalonians 3:1 Wherefore when we could no longer forbear, we thought it good to be left at Athens alone;
1 Thessalonians 3:2 And sent Timotheus, our brother, and minister of God, and our fellowlabourer in the gospel of Christ, to establish you, and to comfort you concerning your faith:
There is only one gospel that stablishes one in the faith, in the Body and that is Paul's "my gospel"!
Romans 16:25 Now to him that is of power to stablish you according to my gospel, and the preaching of Jesus Christ, according to the revelation of the mystery, which was kept secret since the world began,
Romans 16:26 But now is made manifest, and by the scriptures of the prophets, according to the commandment of the everlasting God, made known to all nations for the obedience of faith:
Romans 16:27 To God only wise, be glory through Jesus Christ for ever. Amen.
The gospel of Christ:
1 Corinthians 15:1 Moreover, brethren, I declare unto you the gospel which I preached unto you, which also ye have received, and wherein ye stand;
1 Corinthians 15:2 By which also ye are saved, if ye keep in memory what I preached unto you, unless ye have believed in vain.
1 Corinthians 15:3 For I delivered unto you first of all that which I also received, how that Christ died for our sins according to the scriptures;
1 Corinthians 15:4 And that he was buried, and that he rose again the third day according to the scriptures:
