I suggest listening to some disco song while reading this post. Here is one to get you started.
Okay, here is my outfit in all its blue polyester glory! (alright, it's pretty plain, shh.)
The fabric is just blue, but the texture is oh so 70s. It's just like some of the vintage clothes I have. The discount fabric store in my area had a bunch of this stuff in lots of colors, and it's super comfortable!
I did use a pattern, but didn't want to do a zipper, so I put shirring in the back, as I usually do. I also added the two skinnier straps in back to keep it up a little better. The pattern was Simplicity 2401. I don't remember if I had any complaints about this pattern - It's been a while, but I think it was pretty straightforward.