The main theme of Acts may be the spread of the word, but Jesus is the key player.
Jesus is risen and he reigns. His primary agents in forming and growing his church are the word and the Spirit (David Peterson).
The risen Lord sends the Spirit (2:33), inspires preachers (7:55-56), calls and commissions his witnesses (9:5-6; 22:14-21), heals the sick (9:34), and uses his servants to accomplish his saving purpose in the world (26:16-18).
Where does that leave us? On backs, lying in the dust of the Damascus road, crying out, "Who are you Lord?"