Best advise is to start simple,and cheap.Try a couple (two or three) Green chromis.Or maybe a clown(percula)...Both of these fish are VERY easy to care for,and Very forgiving in a new tank...
Abetter question would be, this is the kind of fish I would like to care for, will it work in this tank, and with this size tank you will be limited on the kind s as many salt waters get BIG somtimes very quikly and will out grow your tank,