When I first started selling my jewelry on Etsy, my photos were terrible. I was very proud of them until I started seeing other peoples' pics! I figured I was in bad need of a effective lightbox. Not wanting to spend a lot of money though, I decided to search the internet for instructions on how to make one. It ended up costing me about $50, including the lights, to make.
I bought some white soft board from a craft store, cut out "windows" in the side and top and then covered the windows with think white fabric. I bought clip on lights which I aim into these windows.
It isn't pretty but hey, it works and it was really cheap to make. If you make something similar remember to keep the bulbs at a safe distance from the fabric so it doesn't become a fire hazard!