Um...for the hakama, make sure you pleat it, since I think they're supposed to be pleated. For the white kimono, you can use pretty much any white fabric you want, since it goes underneath the black one. I'm in the process of making a shinigami uniform, and I used white cotton broadcloth for the white kimono.
I've been told that a polyester blend of at least 50% polyester will do well for the hakama, since it will hold pleats well. But I asked someone at my local fabric store if a 55% linen/45% rayon blend would hold pleats, and she said it would since there was more linen than rayon.
Also... here's a link to a page with lots of Bleach cosplay info:
I hope I was able to help ^^;