A DIY tank is a good idea. I'd make it at least 4'x2'x2' but go larger if you have the room to do so. I would make it tall and build in branches to allow for lots of climbing like taterbug's setup
https://sites.google.com/site/thelizardmadness/photogradient
A socket fixture will allow you to mount a halogen basking light overhead. I would also use a T5 22'' fixture for UVB like this one
http://www.lightyourreptiles.com/22-t-5-ho-fixture-high-output-with-arcadia-d3-12-ho-bulb/ Those two side by side over a main basking area should give you an excellent basic setup and you can add from there if you want to.
As far as building material goes, I would use a non treated plywood. Melamine is popular but it's quite heavy. A good quality plywood should do nicely and then you can stain it and seal it with polyurethane or paint it with a non toxic paint to protect it from moisture.
There are a LOT of options that are good so you can get really creative. Check the DIY and enclosures sections for some ideas. I'd go along this route to start with though and be sure to invest in high quality lighting as a priority in the budget.