i'd say either a blood(or fire)shrimp or a cleaner shrimp
and for stars, you won't see them anyway, so in a tank taht size, i'd say mini brittle stars and micro stars, jsut for the cleaning benefit
for a clan up package, get a detrivore kit, and some trochus snails, or even turbo snails, ipersonally do not like crabs, but others do, tehy do have their benefits too, but in 10, snails do a good enough job IMO
if you get lr, you will get plenty of pods and worms, otehr wise, i'd get them too
HTH and good luck