There are several good brands of batting in the marketplace. I use 100% cotton or an 80/20 cotton blend that has been needle-punched. The benefits of using needle-punched cotton batting is that the batting will not separate or bunch up, even after many washings. When washing use as little agitation as possible or wash in machine with no agitation.
Another batting I like to use is 100% wool. Wool batting produces a light weight quilt with excellent loft retention. I use Hobbs Tuscany Collection which can be hand or machine washed. When washing use as little agitation as possible or wash in machine with no agitation. Too much agitation or steam could cause felting in wet wool. I have have had much success using a front load wash machine.
Quilts with cotton batting are heavier weight and have lower loft; where as, the Wool batting has a lighter weight and a higher loft. The wool gives warmth without the weight. The fiber breaths, allowing excess heat to disperse away from the body.