I used 2.5 yards of a Sew Classic Simply Solid 100% rayon challis from Jo-Ann Fabrics. I think it might actually be the same fabric used in the original Forever 21 skirt.
The fabric was on clearance and the clearance fabrics were all on sale for half off. Between the sale and my employee discount, the fabric cost me about $2 per yard. Unfortunately, the fabric gets wrinkled pretty easily and it is nearly impossible to get all of the wrinkles out.
It took me forever to get the pleats on the front to look how I wanted them to. I had the skirt pinned to my duct tape dressform and played around with the pleats for a few hours. There are seven pleats on the bottom flounce and eight on the top. The bottom flounce is 14.5" long at it's longest point and 6" at it's shortest point. The top flounce is 11" at it's longest point and 4.5" at it's shortest point.
This was my first time sewing an invisible zipper. I accidentally clipped my fabric into the seam allowance and I didn't leave enough room at the top for a hook and eye. But at least it works.