you don't have to go crazy with the cleanup crew. it's up to your personal preference.
if you expect lots of uneaten food hitting the sand bottom, then get the nassarius snails, but otherwise, they don't eat algae...so you might need to suppliment their feeding.
my turbo snails are about the size of a golfball. i would not have alot of these in a 14 gallon tank. they will knock over and re-arrange everything, every night.
i don't even like the hermit crab idea. i think they are poor at cleaning up anything, and they can, and most likely will, kill your snails occasionally for their shells.
i suggest you pick and choose what you want carefully. things you will want to enjoy watching, and things that are more a pleasure, than a nuisance.