For those of you who struggle with texture, know that it's not something that comes quickly. Learning to render different materials is a multistep process, and it's important that you not jump too far ahead before you're ready.
I've devised this rather intensive challenge to help students get mileage in the proper areas, in the proper order, with explanations of what to expect at the different stages. Remember though that this is a very time-consuming challenge - much moreso than the 250 boxes or cylinders. Spread this out over a long period of time, and mix it into your other work. Don't try to do it all at once, or there will be tears.