Most freerolls are easily found and thus overpopulated to the point of being unprofitable.
I play on
Titan and hunt for the private freerolls that have 1:1 or better person to dollar ratio (i.e. 100 people $100 prize pool). I got my main bankroll there by winning one of those and multiplying it, and I use those freerolls and cheap buy in's with money added to supplement my MTT and SnG play.