If you want a reference, I have a 65 gallon and this is my crew:
1 skunk cleaner shrimp
1 blood red fire shrimp
1 peppermint shrimp
about a dozen hermits (i recommend only getting scarlett)
about 10 mexican turbo snails
5 or so trochus (but my blue leg hermits murder them)
5 or so nerites (same)
20-30 dwarf ceriths
3 large nessarius snails
6 of the smaller nessarius snails
And I would say the best "cleaners" are the shrimp, the turbos, and the nessarius snails (for the sand bed). Dwarf ceriths reproduce in the tank. So you'll end up with lots of them, if you want tiny snails all over the place.
But I started with much less. One shrimp, the hermits, and some snails. I gradually added more as my tank matured.