Get yourself a carbon, rigid fork. That will give you the most weight savings right there. Components, you are talking grams, and Deore XT works just as well as XTR. You also won't notice the weight savings of going to a 1x up front (which can also be a very costly upgrade). Switching your fork will save you pounds. Some slick tires, too. Those will save you a little weight...but more so make the ride a lot smoother. I would do wheels last, as I would choose to do your fork before wheels.