For the top, I'd use a bottomweight, probably a sateen or a twill. For the skirt...well, it's supposed to be like a schoolgirl skirt, so I would suggest a similar fabric, but from the drawing, it seems to flow like a lighter fabric. I'd go with a lightweight cotton of some type. Not too light, like a broadcloth, but something really fine and smooth, with a high threadcount. Cotton will get crisp pleats in it. A polyester would also work really well, since it would give you that flow and drape, and polyester pleats really nicely if you heat-set the pleats in place. (you also have the advantage of being able to melt your edges, around all those tatters, so you don't have to worry about unraveling)
Good luck with it! I love militarystuck, so please post pics when you're done.