You can get a 30G and get 3-4 fish and make it interesting by getting a Clownfish Mated Pair, a Watchman and Pistol Shrimp Pair and a beautiful fish like a Royal Gramma. The system is a good size, no need for a skimmer as water changes achieve the same thing. Also you can put some T5's over and then you can get some beautiful SPS
corals and a clam or two.
Small can be just as amazing as large.