klswift

I suggest that you use a thinner batting (natural or poly) just because it will be easier to handle. Thicker can get trickier maneuvering it in your machine. But, it is your quilt. Other than learning a 1/4" seam, most of the rules are more of suggestions. You get to make the decisions and those decisions will improve with experience. Just making a quilt puts you far ahead of most folks. Consider many of your 'mistakes' simply adding design elements. But, not mastering a 1/4" seam, will create hours of frustration and yelling. Have fun!