Okay, so you mentioned boots and pack as essential so I'll skip over those.
HYDRATION SYSTEM
Binoculars.
Socks
Layered clothing
Rifle/bow
Trust me when I tell you, any hunt is ruined if you don't hydrate properly.
I'm not selling any powders or goo, just a solid water system that is safe(doesn't puke if you fall on it or take a thorn, also easy to clean) and plenty of it.
When it comes to food/water, I can go all day without food, but I get nervous if I'm not peeing clear and if the temp is over 70 degrees, it's twice as important. A basic 32oz Nalgene (two of them) is a pretty good start.
Most people I know spend tons more time behind their binoculars than a spotter, plus you have to spend real $$ to get to a level of glass that is useful at 40X magnification. I would much rather have excellent binoculars and rifle scope than a spotter, plus they're cumbersome and awkward. Also, binoculars are very subjective. Don't believe the fanboys when they spout their favorite brand. What works great for one guy doesn't for another. If you see someone post 'you can't go wrong with -X-, you most certainly can.
Layered clothing is pretty important to me. I don't want to own one AMAZING $500 jacket, I want to own layers of synthetic I can shed, dry quickly, and put back on as necessary. I have found MilSpec ECWCS Level 6 outerwear is a smoking deal compared to the Gotta-Have branded camo 'systems' and you have many more fitting options.