Read, Read ,Read - go s l o w. For your size tank, the most $$ put out (all depending what kind of corals you want) will be lights - weather PC's, VHO and/or Metal Halides. Then the other pieces of equipment.
But first of all you said saltwater- is that FOWLR or a reef tank

Because depending on what you want will determine the $$$$$$$$$$$$$$$$$$$$$$$ you will spend. This is not a CHEAP hobby by any means, but if you are handy and can diy, as I have made a lot of the equipment you can save some $$. And like all things that start off as a hobby can be addicting and wanting to get a bigger tank to house all the animals that you have bought and traded for.
More $$$$$$$$.
I started off with a 100 aga from my freshwater days added a sump and fug and now I'm planing for a bigger tank. In wall plywood 350+. Some of the pieces of equipment I can take from my current setup and use them for the new tank. But everything I will have to make, bigger.
Back to the orginal question; is your tank going to be Fish Only With Live Rock (FOWLR) or a reef tank?