Well, Many people choose to have a Sump/Refugium. These hide equipment from the main tank and the refugium helps keep the nitrate down meaning less water changes. Usually a Refugium has a Sand bed and a type of algae. Pods
are often cultured in the refugium to be sucked by a return pump into the main tank for fish to eat. To get good water, a RO
unit is recommended. It doesnt have to make 100GPD, 30 or so will suffice for most people.
You also will need a good light for coral, The type depending on which corals you want. Hard corals need higher light than Soft corals and zoas. Zoas are a good starter coral.
In the sump a skimmer to remove excess waste is recommended, It helps lower the ammount of waste that becomes nitrate. Nitrate can also be removed by having a DSB
(Deep sand bed) Where Anerobic bacteria turn the nitrate into nitrogen.
Look on local reef forums for a tank setup. You can usually get them really cheap. You could get a whole tank with rock and sump for a few hundred. Try to get a Reef Ready tank. It makes adding a Sump alot easier. People also sell coral frags which are pieces of a large coral which grow eventually. Corals on forums are alot cheaper than most LFS
. Live rock and misc equiptment can also be found quite cheap.