So I found an awesome pair of shoes ($4.98), a magician's costume ($1.98) and an XXL shirt that was somewhat sheer...
And I determined that I wanted to do the best I could to create a costume with as little sewing and as little effort as possible! Here's what I did:
Magician's costume: I cut the sleeves and collar off. I hiked up the skirt, letting it pleat naturally where it did. I cut a strip of fabric from the sleeve and used it to tie the skirt up that high just above the slit (cutting a hole in it to thread it through). I also cut strips of fabric from the sleeve to tie around the straps to give it a different look. This made up the underdress.
Big shirt: I cut the sleeves and collar off. I cut a slit from neck to navel, and then fringed the bottom. I tried it on over the underdress, and tied the sleeves to the underdress to give it a uniform look.
And the final result....
I completed the look with black tights, the shoes I got (I made shoelaces from the sleeve off the big shirt), a feather boa I happened to have, and some awesome jewelry I got for $1/item. Oh, and of course, lots of awesome flapper-era makeup. It was the bee's knees!