Yes, the Gita is a gospel of action. Krishna exhorts Arjuna to fight, to do his duty, to be a karma-yogi. But it is also a gospel of knowledge. No action is complete, or desirable, without knowing why, how and when to act. So Arjuna has to be jnana-yogi as well. Krishna places a vey high value on knowledge that crystallises into wisdom. But knowledge is not complete, or desirable, without shraddha, faith, spontaenous feeling, which in its best form becomes bhakti or devotion. Arjuna must learn to be a bhakti-yogi also.
So in the concluding Canto, the paths of action, knowledge and devotion merge in a single direction : moksha-samnyasa (which means salvation through self-surrender, or renunciation, and which is the title of the Canto).
'Act one must', says Krishna (shloka 11), but act only after learning from Samkhya philosophy that ' work is ruled by five causes : matter, agent, motive, motion, fate'. And finally, 'have faith in me : worship me' (madbhakto mam namaskuru). That is the secret, for that enables a person to discover true self-dharma : 'Own's own dharma, however imperfect, is a safer guide than the dharma of another, however perfect' (Shloka 47).
The key shloka, the final advice, is in number 63 : 'This is the subtle wisdom I give you. Think it over. You are free to choose' (yathecchasi tatha kuru). If the ultimate goal is freedom, the means too must be freedom to choose. 'Him whom I love, I would make free even from me'.