Have you tried making a pillowcase dress before? I did, and I was NOT happy with the results. The dress was a huge shapeless sack on my skinny little girl. Not as cute as I was hoping. But I found a super cute pillowcase at a thrift store that I knew would be a great pillowcase dress. So I followed the basic tutorial found HERE, modified the idea and came up with this:
It has an empire waist to give it some shape. So much better than the sack dresses, in my opinion. And the elastic on the neckline makes it easy to slip on with no zippers or buttons to mess with. My kind of sewing!
To add the waist, I just made the bottom rectangle of fabric larger than the top bodice part of the dress, giving me room to gather it a bit. Very simple to do, but it totally changed the shape.