I'd suggest that if you to piece it together as you're able to afford to, that you start by purchasing your live rock and a good skimmer. Afterwards, the next purchase should be your lighting. You can do NO fluorescent lighting for just fish. You will have to upgrade your lighting before going for corals, anemones or clams though.
You can also save a lot of money by purchasing base rock instead of ALL live rock. You can also save money by purchasing non cured rock. The curing process will take a bit longer and can sometimes be pretty smelly...lol. However, it's A LOT cheaper. If you do go the base rock route, I'd suggest getting 1/2 base rock and 1/2 live rock. The base rock will eventually turn to live rock just fine. I wouldn't skimp on a skimmer either. It could be the best or worst investment you make.
You've mentioned, twice, a 4 foot tank. Can you be more specific? It may help in determining your equipment needs. Is this a 55, 75 or 90 gallon tank? It'll make a big difference with your amount of live rock, your skimmer and eventually make a difference in your lighting as well.