Well, I do a lot of dyeing and I do order my dye from Dharma. I am not sure but Michael's may care the procion dye. This is what you want.
Any good quality white fabric or unbleached muslin will really dye well. It has to be 100% cotton. I would really suggest the unbleached muslin.
Be sure and check out Dharma's website for information regarding the dyeing. They have a lot of information.
You talked about a coupon so I wonder if you are talking Joanne's?? Check there for the procion dye. They just may carry it.
Sorry I couldn't be more help. Yes, the dye and dyeing supplies do start running into a quite a bit of money.