To be honest, you probably shouldn't get many (if any) hermit crabs. They'll bother your corals and kill your snails. Maybe get two or three of them, if you really like them. Astrea, nassarius and cerith are all good snails.
Anemones are the kind of thing you really need to think about. Clowns don't need them, and they're very picky and can be hard to get going. They need excellent light and excellent water quality, as well as feeding a few times a week. There is also the problem with corals. If you get lucky, you'll get one that stays put. If you're unlucky, you'll get one that goes into the powerhead and nukes the tank or one that goes wandering and kills half of your corals. They are pretty cool creatures, but definitely something you need to plan for.