I just made DD2 a long skirt and didn't use a pattern. Just two rectangles and then encased a wide piece of elastic. I used about a meter of fabric as it is long on her (to the floor) and very flowy. I would get a yard at least and then you have spare for playing with.

You could get some calico from spotlight to test your shape/pattern first so you know that when you cut your fabric you're doing it right. I do that before I cut into expensive fabrics. That's how I create my own patterns