I don't have room to store a whole roll of it, so I buy packaged batting. I use Hobb's 80/20 or Warm & Natural. I can get both brands at Joann's or online. Hobb's I can sometimes get a great deal at Michael's with a coupon. If I can't find at Michael's, I usually order from Connecting Threads and buy a few so I can get the free shipping. Usually even with a coupon, it's more expensive at Joann's. I do occasionally get it there in a pinch though. I've found the quality to be the same for the same brand no matter where I've purchased it.
Consider the quilting you want to do before you pick one. If you want to quilt further apart, Warm & Natural lets you quilt every 8-10" or so. Hobb's is every 3-4" I think. I prefer the 80/20 blend and it handles much like the Warm & Natural Cotton. I've never used the wool. I did use Quilter's Dream Orient once and loved it, but it's 2.5-3x as expensive, so I haven't bought it since.
I spritz it with water and put in the dryer on low for about 10 minutes. It helps with the wrinkles.