I've made my share of furniture.. and i've noticed that you can use cheap materials but you will get a cheap look.. i used MDF and plywood.. they work ok but they don't look very nice.. they don't stain and sometimes they are horribly heavy.. then i used 1/2 in hardwood plywood.. which stains very well and looks great... However, is very expensive and it extremely heavy... you can see this in my shoe cabinet instructable..
So after doing a bit of looking around i found this great material called tri-ply underlayment.. it looks like is plywood with a hardwood thin veneer in both sides.. This material is great because is very lightweight.. it stains very well and is extremely cheap!!!
you can buy a 4 by 8 sheet for like 8 bucks.. However, because is so lightweight is not very sturdy so it will definitely need some kind of skeleton reinforcement..
Here is where my second very cheap material comes into the picture.. 1in by 2in by 8ft furring strip.. this strip is plenty sturdy and plenty cheap.. you can buy a strip for 89 cents at lowes.. also at home depot.. but i found the one at lowes is better quality and sanded a lot better.. this is no advertising for lowes.. since i buy the tri-ply wood at homedepot.. and i hate them both equally..
Anyways i usually plan my cuts according to the 4 by 8 ft tri-ply sheet.. i also pray i get a very patient and very accurate cutter at homedepot.. this is a hit and miss so i hope you get lucky..
My idea was to have the lower part of the table be 4ft.. and the top part be 2ft.. then after a lot of thinking and planning i lay my cuts in a piece of paper (please account for about 1/4 inch of waste due to the saw).. take it to home depot and get as many of my cuts done there so i dont have to do much at home.. also it helps me fit the wood in my tiny toyota celica... i buy as many 1 by 2 by 8ft furring strips and about 3- 1 by 4 by 8 ft furring strips for the legs.. i dont cut them.. i cut them at home.. and drive with part of them sticking out of the window :)