In order , for me, your needs may vary, but generally speaking these are key items to focus on, as many have stated. Each person's list varies, but usually not much, dependent on what hunt and where and how long of course.
Pack/Boots- still haven't been able to separate which one is more critical to me. lol
Sleeping pad- a good one makes or breaks the trip comfort
Base layer- good stretchy merino bottoms and top
Rain gear top- I only pack a top, never use the bottoms
Chest rig- bino harness is often over looked, but a good one has space for everything you need for
Water System- decide if you want to carry the weight of a filled bladder, or the weight of filtration/pump, in a filter/steripen, nalgene bottle configuration. Just depends on water availability and food processing more than anything. Dehydrated meals take too much water from my nalgen, IMO, so I went with a MRE type meals, which require way less water needs.
lastly- your emergency needs. Like a INreach or SPOT etc.
Things that everyone uses- emergency kit, maps, on paper or phone, I don't trust the GPS watches for main use, but only as a redundant system. Lighting, charging batteries. I quit using AA, AAA years ago. Everything is now rechargeable off a battery bank of around 28,000. To me it's worth the weight, and yes they are heavier than desired.
I'm sure there are more, but this is close to what is needed as far as what to really look at. Avoid bad imitations to these items. A good sleeping bag is nice, but honestly, when you can just use a good pad for decent warmth protection and comfortability and sleep in clothing that is a place to save lot's of $$$.