There are no quilt police here but this is what is pleasing to my eye. I take a component of the blocks. Say a block is 6 inches finished, I will either do a 6 inch single border or a combination of borders that equal 6 inches. That is proportionally pleasing to my eye. Again this is from my grandma who taught me to quilt. However you need to do what seems correct to you. This is just my method.
