Welcome to the forum MsJO. If I'm doing the math correctly the 9 8" squares will result in a 23" unfinished or 22.5" finished block size. Being an international group I'm surprised the measurements aren't metric instead. The best advice I can give for the fabric is that since you're probably going to have to buy more than you exactly need for this block anyway, choose fabrics in colors that you like too. That way you will be able to find uses for it later. The good thing is solids tend to be less expensive than prints and (at least to me) are easier to find uses for. Just think of it as building your stash.
Rodney