I think the Flying Instructor's manuals make more sense when you're actually doing the course (and afterwards). Before arriving for the FI course I was told to re-read all my PPL Flying Training Books.
On the course, you learn how to break each manoeuvre / lesson down into its constituent parts so you can demonstrate and teach it. Re-reading your PPL training books will make you familiar again with this.
Best idea is to telephone the FI school and ask your Instructor what they wish you to study first.