I would say, since you don't know what you will be doing with them, cut them the biggest possible. Just get rid of the parts that you know you will not be using, such as seams and pockets (and even those you could use in the future). If you limit yourself to a certain size and find out later that you need just a two inches square but the fabric is not available because you threw away a sleeve, you may end up pulling your hair later. Don't ask me how I know. I say save the biggest possible to expand your future possibilities but also save the little ones for emergencies. You could use baggies to save all the pieces of the same color together.