It will take some time, but the social community freerolls are often the best for limited player pools.
888 has a ton of community events, you'll actually have to be somewhat part of a social community. 😉
Seen a lot of angry freerollers taking their rage out because a password isn't zero effort to acquire.
ACR as well, very good community freerolls for bankroll building, lots of penny buy community events with $200-500 dollar pools. Some take a bit of effort to get a password.
Some of the best payers if you can run deep, the ones that pay out top heavy.
Some of the ones that feel like a huge waste of time to me, any short stacked super turbo type lotteries, at least its a quick donkey experience, pick a decent hand and send it, repeat, not much poker. Gotta play them, though, some really good prizes if you are building from zero.
Aside of that, you will definitely find a good volume of normal freerolls on cycle.
888/ACR/
partypoker/WPT Global/Jack Poker/GGPoker, they all run daily freerolls with $100-200 pools on average, a lot of them have a big prize distribution and 800 players or so, so if you run average, .18, .20, maybe a deep run, .80, final table, few bucks.
Those are just fine, too, put that FR money on some .10 sats, .10-.50 MTT's and start laddering.