I have a snail breeding tank. It's a 5g tank, and I have a few male fancy guppies in there to keep things interesting, since they don't eat snails at all. I just make sure to drop in some algae wafers and such for the snails. They gather around the wafer and have 'meetings'. It's hilarious.

I have some java moss, ecocomplete substrate, small heater, Whisper internal filter, and a small cave ornament. But really you can go with the bare minimum and it'll work just fine. Some snails do like to have plants to lay their eggs on though.
Pond snails are my favorite for puffers, since they stay very small. Ramshorns are also good.