really depends on what your needs are. i'd say a safe bet to start with would be 5-10 each of astrea, margarita, cerith, and nassarius snails, plus 10-20 or so reef hermits.
peppermint shrimp are a good idea for aiptasia control and a cleaner shrimp is pretty much considered standard. sand-sifting starfish might be another invert to look into, although you may want to hold off on that until your sandbed becomes more established. if you haev any bubble algae you could pick up an emerald crab, but they can get rather large and may eventually attack small fish if they get hungry.