Welcome to the forum. please feel free to ask any questions you have. Our collective wisdom is actually pretty impressive. I have visited other marine forums and this one just plan rocks.
As for your fish question, you are looking at about one, 4-inch fish or two, 2-inch fish. a pair of firefish would look nice. royal gramma would also be nice. a royal dottyback looks similar to a gramma and is a good fish. not many people like the pink skunk clownfish, but that is always a nice addition to a smaller tank. Lots of options, up to you. Do your homework before deciding on a fish. Tends to take the headaches out of the future.
-Doc