Galatians has three sections: autobiography (chps 1-2), theology (3-4) and praxis (5-6). Simplied of course. The opening section of the autobiographical argument for Paul’s gospel has several references to “gospel” and “gospeling”:

11 I want you to know, brothers, that the gospel I preached is not
something that man made up. 12 I did not receive it from any man, nor
was I taught it; rather, I received it by revelation from Jesus Christ.

13 For you have heard of my previous way of life in Judaism, how
intensely I persecuted the church of God and tried to destroy it. 14 I
was advancing in Judaism beyond many Jews of my own age and was
extremely zealous for the traditions of my fathers. 15 But when God,
who set me apart from birth and called me by his grace, was pleased 16
to reveal his Son in me so that I might preach him among the Gentiles,
I did not consult any man, 17 nor did I go up to Jerusalem to see those
who were apostles before I was, but I went immediately into Arabia and
later returned to Damascus. 18 Then after three years, I went up to
Jerusalem to get acquainted with Peter and stayed with him fifteen
days. 19 I saw none of the other apostles-only James, the Lord’s
brother. 20 I assure you before God that what I am writing you is no
lie. 21 Later I went to Syria and Cilicia. 22 I was personally unknown
to the churches of Judea that are in Christ. 23 They only heard the
report: “The man who formerly persecuted us is now preaching the faith
he once tried to destroy.” 24 And they praised God because of me.

First,
Paul’s gospel is not man-made but comes “by revelation from Jesus
Christ” (v. 11-12). This means he thinks his opponents’ gospel is
man-made: the Christ + Torah observance (or commands within the Torah)
is a man-made gospel.

Second, Paul’s task is to “gospel” to the
Gentiles (v. 16). And he didn’t need authorization from Jerusalem —
the man-made approach — to preach this gospel.

Third, Paul sums
up his opponents attitude to his task with this: “The man who formerly
persecuted us is now preaching/gospeling the faith he once tried to
destroy” (v. 23). The word “faith” is central to Paul’s gospel.