First off, if you get a snowflake eel he will eat your clownfish, you need to decide if you want a preditor tank (lionfish, eel, trigger), or community tank (clowns, gobies, tangs). You are severely limited with the amount of fish you can add. You can probably get away with a couple of clowns and gobies. To get a good idea go to
www.liveaquaria.com and look at the fish, try and stay with marine fish for begginers. The good thing about liveaquaria is they tell you the recommended size of the tank you should have, for example, most tangs are 50-75+ . I beleive in a 30 gallon you can get away with a dwarf angel which is pretty cool. Also look at the compatability chart to get an idea of what you can keep together. Also check out the articles section of this forum, and read as many threads as you can, you dont want to jump into this. I researched night and day on this forums for at least a month before buying anything. As for equipment you are gonna need powerheads, heaters, protein skimmers are recommended, and some sort of filtration, i use liverock and a deep sand bed as my filtration method, some uses some sort of filter, really depends on where your heading. If your serious about this i would get a bigger tank, i got a 50 and am already regretting not getting a bigger tank, plus you success would be better witha bigger tank, more fish, and a better variety of fish you can add. Good luck and keep us posted.