it's true that fish selection is limited but you still have lots of options! and the fish that you can have are super cool. I am partial to the royal gramma. and clowns are a good standby. tailspot blenny, gobies, all really cool. lots of cool crustaceans you can do too. porcelain crabs tock, as do shrimp. and you can do a nice mini coral reef as well if you want! just pick hardier corals, like mushrooms or zoanthids!
I have a ten gallon, and knock on wood it's gone perfectly so far. so rewarding and maintenance is so easy. I do a one gallon water change once a week. I picked a ten gallon because it needs to live in my dorm, but I am very happy with it!