Turkey gravy - make ahead?
3-4 days would be safe for your make-ahead gravy. I usually make mine a couple days before Thanksgiving. I've kept leftover gravy in the fridge and used it for over a week afterward without it going bad.
Other things you can make ahead: Cranberry sauce, yams, stuffing (1-2 days). I make potatoes au gratin a couple days in advance so that it is all ready to pop in the oven.