I just used scrap fabric, cut into strips ( each set longer than the next) and gathered slightly, with an elastic waistband.
The fabric is a simple, cotton broadcloth. The gingham that the bottom tier is made from was actually quite sheer, so I had to be careful not to bend over too far when wearing it.
I grew out of this skirt quite quickly and ended up selling it to a friend. I hope she's enjoying it.