I cross-posted this on my fashion blog, you can check it out here, as well!
I used an old pattern, New Look 6401 (view B), and $40 worth of polyester fabric from JoAnn (I'd much prefer silk, but I was on a budget). As I usually have to do with commercial patterns, I took the waist in one size and let the hips out one size, and I also had a weird gaping issue along the neckline which I solved with some pleating at the straps. I hope it doesn't look like a cheap polyester gown. :-)