Yeah, I hear you on being broke! This is an expensive hobby when you are just starting off. The snails are less than a buck a piece (minimum order 12), so I'll bet you can get 12 for under $25, but I can't know the shipping cost for sure. AAG could give you an estimate.

I assume you do not live in my area (Los Angeles)...I'd happily give you 6 nerites. Mine are eating so much algae that I don't think there's enough for everybody else in my tank.

One post said that a simple test for whether or not you have enough flow is if ALL of your plants are swaying. If some are standing still, you are probably lacking. If a C-220 has 220 gph, that's not too bad for a 30G tank, though many here would do more. With your extra filter going, I'm sure you're fine, as long as the flow isn't being blocked in too many places. I have some plants that really need to stay pruned in order for me to have enough flow.