You can do a saltwater setup cheaper but its hard to do cheap. You could start by buying dried out base rock and and just a little liverock to seed the base rock. This could save you hundreds of dollars. If you plan on keeping corals or an anemone you will need special lighting. If you are going to do a fish only with liverock (FOWLR) than you can use any lighting you want. A skimmer isn't needed for that size of a tank, if you keep up your water changes, but it will definately help keep all your water parameters in check. Using ro/di water to make your water would be the best. You can get it at the LFS or you can buy your own unit. If you don't use ro/di water you might end up fighting algea. Filtration in saltwater is different than freshwater. In most saltwater tanks the only filter you will see is a protein skimmer and maybe a filter sock. The filtration in saltwater tanks is mainly done by the liverock and the protein skimmer. Also a way to save money is buy things used. Look on ebay, find a local reef club, check the classifieds here and on other sites. The thing with saltwater is that it takes time and requires patience. I suggest you buy a couple books and read as much as you can online about saltwater setups. There are many different ways to run a successful saltwater setup. Read a lot and ask a lot of questions. Mistakes can be very expensive in this hobby.