I like to make my own stock for the gravy a week in advance. I buy inexpensive turkey parts (necks, wings, drumsticks) and roast them with onions, carrots and celery until everything is nicely browned. Then I drop them into a large stock pot and simmer for 8-12 hours. Drain the stock freeze it until Wednesday, then thaw it in the refrigerator while the turkey brines.
I also like to make a light roux in advance (Wednesday night) and refrigerate that until I am ready to make the gravy while the turkey rests.