live rock.
Probably you will be getting base (and live rock) live rock goes on the top but it need time to cure as the base rock is rinse and dump in.
So if you plan on using LR (which most everyone does ATM) You can get the top curing on the bottom till you have the coin to get more base rock to stick under it.
There ya go that should keep ya busy for a ;arge chunk of change.
Tank with overflow and sump if you plan on one (highly recomended)
Salt
water
pump
Skimmer assuming you want to use one (most peeps do).
LR
LSand
Base rock