ummm i think the cube cost me 189 from fishtown, first chamber i left the sponges that came with it, second chamber live rock rubble and carbon and i bought the maxjet 900 online for 20 bucks (upgrading the waterflow).
The live rock i bought from fishtown which i think was 4.99/lb and the sand was another 20 or so,
I don't make my water.. i cheat.. i buy it :p but i have a 12g so that works for me.
oh and a heater and thermometer (don't remember how much) and i think thats it
i would ditch the sponges in the 1st chamber and see if you can fit in a nano skimmer...if not just remove the sponges. They might be good while debris are floating around in your tank, but they will just add to the nitrates in your tank as the stuff they catch rots.
You don't need a sponge in a reef tank like you do in a FO tank as the LR acts as a natural filter...
Also make sure to rinse out your carbon once a week or so for the same reason.