I think you can do this with a medium wig and a long piece.
You can get the Jereth from arda. It already comes in lovely colors and is layered. All you have to do is trim it a bit and fluff the bottom. Then get a weft in the same color and cut it so the wefts are shorter width wise, then sew a few in and make the longer part. I think that's a better looking way then cutting an extremely long wig..
Also, this is a very thick wig. Great for styling