Not sure bout wood but you may think about a used 20 gal fish tank you can usually get on for 20.00 and I just built a dual layer stand and for just 1 4x4 sheet of 3/4" plywood it alone cost me 19.00
Here is a couple of mine it has sand(which I don't recomend you use). I'm also setting one up as I speak That will have a slight layer of sand but solid Tiles ontop so no sand will be showing I'll post that one after I get it done.