What material and how much material should I buy?
Wash them without any softener!
It would be easier to advise how much material to buy if you gave us your measurements.
I would highly suggest getting a pattern. I found a pattern for a robe and made my son a LOTR robe. Think it took 4 yards. IF you won't get a pattern I would suggest getting muslin and making a trial robe first. Muslin can be a dollar a yard. don't cut into expensive fabric till you know it will work. fabric as thin as t-shirt material is way too thin. and fleece is really too thick. fleece can be heavy and when sew into a robe or cape can start to droop. For the LOTR and SW costumes I have made I used a thicker woven cotton.
