Here is a photo of my reindeer:
I use 3/8" grosgrain. I don't have measurements for the face pieces, as I just eye it according to the size of the child who will be wearing it. You just take the piece of ribbon, fold it in half and put a thin line of glue where the ends meet. I then glue those pieces onto the clip and add the eyes, ears, nose and antlers. I use the gold glittery pipe cleaners for the antlers now, but this is an older photo.
Hope this helps a bit. Sorry I couldn't be more specific.