Personally I favor more snails and less hermits. If you have a 30 with a sand bed try this:
5 nassarius snails
5 cerith snails
10 trouchas snails
5 stometella snails
5 margarita snails
5 scarlet reef hermits
Shrimps are nice and decorative but don't add much to a cleanup crew.
Other options are a fighting conch but I would not add more than one in a tank this size, turbo snails (natures bulldozers so if you don't like things getting knocked over don't have them), astrea snails (good cleaners but seem to die fast when the fall over)