I have a few plots involving the main character, but the action mostly involves side characters and his involvement really amounts to his reactions, his involvement with side characters (typically friends/family), and what he learns from them. I'm really stumped as to a "central" plot or even how to otherwise connect the others. Would you please make some suggestions?
So is this more of a character driven story as opposed to a plot driven story? As a poster said above, you still need a plot like he's trying to find peace for walking away from his faith or his mom is upset and refuses to talk to her. Have you seen the movie, Real Women Have Curves. It's about a college aged woman works in her sister's sweat shop and she wants to go to college and no longer work in the sweat shop. Mom and sister pretty much have drama attacks over it and try to talk her out of it. but at the end, the girl goes off to college despite her mother sobbing in the bedroom and playing the victim.
So what does your character what to do? What is like someone said above, the pay off? What is he trying to find? Redemption? His own path? Peace with freaked out mom?
character driven stories are just that, the character drives them, but you still need a plot. So now you need to talk to him and see what does HE want? Once you find that, you'll find your plot.