Need Some Sewing Help

I am going to make Infinity Dresses for my bridesmaids. The idea is easy, the pattern can be found at Rostitchery  and is completely adorable. I have seen it made in a variety of versions, long and short but I just need some help on how to do the long version.

I have gotten far enough to know a circle skirt just isn't going to cut it and it is going to have to be A-line but that is as far as I have gotten. If anyone has any patterns/ideas for a nice skirt that will give me that grecian/fluttery/pleated without being pleated look it would be much appreciated! Just for a little background on the dress; it is essentially just a skirt sewn with a waistband, that has 2 large, and slightly overlapping fabric straps that can be wrapped in a variety of ways. Because it is sewn with stretchy fabric, such as satin jersey, it stays in place.