It is suggested that it is best to start in the center, of the quilt. If your questions is where to start on your practice sandwich, it really does not matter. Don't forget to breath and try to relax. FMQ takes LOTS AND LOTS of practice, hands slow, machine faster. Each one of has our own "sweet spot" for quilting. That is the special area where you feel comfortable and your stitching looks nice (hopefully).
Good luck