I have written up the disco helmet and bra in separate instructables, which are linked to in the last step. This instructable focuses on how to make the silver top and leggings. As two basic pieces, these instructions could be used for any stretchy top and bottom for costumes or everyday wear. I didn't document it at the time, so have made diagrams to explain the process.
The only things you will need for the top and bottom are silver fabric, elastic, and a zipper. Take care when choosing your fabric! I used a relatively nice 4 way stretch spandex. Some of the silver lame out there is cheap and crappy, and can run like pantyhose. I would recommend using the type of silver created by many dots of foil vs glitter or solid foil (which cracks), as it is usually higher quality. Here are some examples if you can't find anything suitable at your local fabric store, all from the most awesome spandex store ever, House of Spandex in NYC:
Laser Foil Dot
Step 1: Leggings - Pattern Pieces
One thing to keep in mind throughout the whole sewing process is to accommodate for stretch. Straight seams will break - the ideal tool for this project is a serger, but if you only have a standard sewing machine, adding some zig zag to your seams will give them a little room to stretch. Some sewing machines also have a "stretch" mode.