Paul uses the word “gospel” one more time in Colossians (1:23) and once in Philiemon 13. Here is the context for Col 1:23:

21 Once you were alienated from God and were enemies in your minds because of your evil behavior. 22 But
now he has reconciled you by Christ’s physical body through death to
present you holy in his sight, without blemish and free from
accusation- 23 if
you continue in your faith, established and firm, not moved from the
hope held out in the gospel. This is the gospel that you heard and that
has been proclaimed to every creature under heaven, and of which I,
Paul, have become a servant.

Again, the gospel is connected here to hope.

There is a chain of connections here:

1. Alienation from God in mind and behaviors.
2. Reconciliation through Christ’s “physical body” in his death to God (in mind and behaviors).
3. The aim of this work by God is holiness.
4. The condition of this work is persevering faith.
5. All of this is Paul’s Gospel.