For a cleanup crew, I like to think about it as an ecosystem, and what exactly needs to be cleaned. I like the crew I have, it works well for my tank: 12 smal turbos, 3 larger snails (cant think of their name off hand), 3 emerald crabs (great for cleaning all the "holes" of live rock and crevices-these guys do wonders!), a coral banded shrimp, 5 scarlet hermits (small enough to get into crevices again) and I have 3 large hermit crabs. Works well for my tank, but others may have different crews. For the hermits, remeber to get plenty of shells for them to grow into!
I have crushed coral, so if you have a sand bed, Ithink you may need a couple of things I don't need because of my substrate.
Ask around for that specific need.