We have a little table top stand (about 1 foot by 1 foot) as well as a big playstand and they both are made out of PPVC. The ones for sale are so expensive and IMO it's much easier and cheaper to make your own. There are lots of links in the DIY section that show different playstands that people have made to give you some ideas.

You can use wood (untreated pine works well) or PVC and the links etc. that hold toys and stuff in place should be stainless steel.
It's great to have a stand in a different room (from the cage) so that she has a place to go to while your busy doing other things, but she can be with you at the same time.

Casey also has a 'playground' on top of her cage including a boing hanging from the ceiling... she spends a good portion of her day playing up there.

Good luck and if you decide to build one, happy building!