Since you seem to me relatively small projects, buying fat quarters would give you a wider variety of fabrics. However, if you find a fabric that you really like, buy as much as you can, because it probably won't be there when you go back. Don't discount cotten dresses, blouses, and men's shirts in thrift shops. After cutting the seams off, you've probably got a half yard of fabric - don't forget to launder before using.