Whenever I'm out of the gym for an extended period of time for whatever reason, the first most important factor for myself is easing back in to it. Your body will be weakened and not expecting an intense workout, so go easy for the first week (you'll no doubt be very sore, even from lighter workouts than you're used to). You may find that coming back from surgery it takes longer to recover from workouts as well because your body is still focused on completely repairing yourself.
Getting back in to routine properly and re-forming some habits that you may have put on hold will be very beneficial to streamline your results. Once your daily gym (and rest days) routine is back on track, start focusing on your diet and supplementation.
Personally, I'd first focus on protein consumption, then veggies, carbs and fats to follow.