That's a great design
I like the way you handled the lighting... should really help keep it cooler inside.
I made one when I started collecting orchids several years ago. Also on a budget, I made it out of a cheap wood frame and plastic sheet sides and back... but I splurged and bought plexiglass for the front (after 6 months, actually).
This is what it looked like. It needed more lights in the top section.
Unfortunately, I outgrew it pretty quickly. The following year, I tore it apart to make some benches to grow under HID lights, and then tore those apart to make room for better ones....
- Matt