Basically you can use tubs stand alone or in a rack system. You can build your own rack pretty easy or you can buy a cheaper one (sometimes can find a used one locally) or an expensive one that's geared towards pros.
For cages, you can build your own or you can buy them. If I were going to buy one, I'd get something PVC and stackable so you can add on later. If you build with wood, you have to seal it to prevent warping and swelling. With cages that are screwed together with multiple pieces, you want to make sure and do a smooth job sealing in the corners with silicone otherwise urates will get stuck in there and be a real headache to clean out.
Personally I would pass on a wood cage unless you're really going to seal the thing with polyurethane and a epoxy topcoat and I'd probably pass on the fish tank, too. I'd use a tub or PVC enclosure. One interesting idea is the wooden cage/fish tank combo
see this