Depends on what you want to keep. Skimmers are an important piece of equipment. Sumps are nice to have, but not necessary. They keep things out of the display tank, like heaters, skimmer, other filtration. You can always do a hang on tank skimmer, powerheads for circulation, and lights (type depending on corals you'd like to keep). A great book is The Conscientious Marine Aquarist by Bob Fenner, and will help get you understanding terms and what goes into setting up a tank. It covers a lot of information - I highly recommend it. A lot goes into setting up a reeftank, so doing your homework before set-up will save you a lot of money and aggravation down the road, and will allow you to truely enjoy this awesome hobby. Also, things like test kits, hydrometers or refractometers, salt, heaters, RO/DI water...are often overlooked at the start.
Do you picture yourself keeping corals? Any fish you feel like you definately want to keep? Be sure to ask questions as they come to you, and we can help you figure out if they'll work with what you have (or will have). You've found a great resource, and the members here will help you out with their experiences....they've always been a big help for me.
