Mistarose,
Think about getting the "Flight Instructor's Handbook." That will go through ALL of the Fundimentals of Instruction (FOI). The GLEIM FOI and FIA (Flight Instructor Airplane) test prep books. Virtually EVERY book that you have used for your PPL and Commercial Cert. you will use for research and making your lesson plan binder.
Now as far as your lesson plan binder goes, that is up to you. I borrowed a lesson plan from my instructor just to see how one would work/flow. Then I made up my own. You could do the obvious - borrow your buddies folder, and change a few words. BUT think in the end - will you really be proud of something that you copied and edited, or would you be proud of one that you started from scratch? Not only will completing your own lesson plan folder make you feel good, but it will also force you to delve into the material. You will be refreshing your memory from your PP days, and reviewing your more-recent commercial maneuvers/procedures. It basically makes it a little bit easier on you in the long run. Anyway, good luck with your checkride (Comm) and good luck with your CFI. Just remember, nothing is more rewarding then passing on your passion for aviation and watching the perverbial 'lightbulb' go on in their head. It always brings a smile to my face...
My 2 cents...
D