I'm kind of surprised you can't get a whole layering system from Sitka, but there is a lot of good advice already listed. I am a fan of the Sitka line and have used the brand for years in some nasty terrain, but they are kind of expensive.
I would recommend some good glass (as others have) and also a good rangefinder with angle compensation. The western hunts may present some longer shots than you are used to.
As for water, I use a Katadyn My Bottle purifier bottle and it works OK. My beef with it is the straw/hinge isn't designed well IMO.
Hope that helps.
Regarding clothing, try eBay, tons of good deals this time of year. Set up a search for sitka/kuiu gear, some real bargains to be had.
Another thought Dan, take a look at the Nimrod Pack systems Pinnacle lumbar pack. I use one, and love it. Super comfy, holds more than you need, and I pair it with a hydration bladder from Eberlestock. My only complaint is that it's difficult to strap on a quiver. I detest having one on my longbow, and haven't found a decent arrow-carrier yet. If you're not spiking out, no sense in hauling more junk than you'll need!
First off research and get good boots and socks!!! Boots more than anything can make or break your hunt. I have seen to many hunters have a terrible hunt because they get blisters and can not traverse the mountains. To me this would be the best money spent. Personally I like the sitka gear, first lite and Core4. You don't have to get all one brand for it to do a great job. Merino wool is the heat and all I wear for layering from socks, upper body, lower body and briefs.
Merino wool, down, water resistant but quiet outer layer, good boots, good glass, pack light. - that's it in a nutshell.
Kuiu has black merino thin t-shirts for $35 short sleeve, and $40 long sleeve. best buy on the market
Cabelas meindl boots are awesome and the warranty is great. A good boot with a bargain price is the cabelas outfitter pro.
I use an eberlestock pack Blue widow(bulletproof) but am considering a KUIU for the lighter weight. If you don't need to pack meat then use a lighter weight daypack (I use a Sitka flash20).
Sitka raingear or new Kuiu guide raingear is worth every penny. The cabelas stuff wont last and takes too long to dry the outer fabric.
My base layer is Firstlite merino T (or now kuiu) , and Firstlite 1/4 Zip long sleeve, then usually a Sitka longsleeve 1/4 zip.
I use Sitka ascent pants, and a 90% jacket . A Kuiu superdown jacket is replacing my Sitka Kelvin insulating jacket. I wore the Kelvin jacket under my 90% jacket when the temps dropped. The kelvin jacket outer shell is noisy and the new Kuiu is a superior product. FYI I just sold my Sitka raingear for the new Kuiu stuff.
more....Havalon knives, I carry the fillet and torch with extra blades. Primos pack bugle, little green primos cow call (called Cowtalker, cowgirl? maybe), 4 game bags, surefire aluminum headlamp, surefire aluminum flashlight ( I've learned that if I can buy something made out of metal I buy it as everything made out of plastic I break), extra batteries packed in a cigar tube, 2-bic lighters, electrical tape. I use the aquamira water bottle with filter and nasty Colorado beaver swamp water hasn't killed me yet. Ive owned lots of packs and will never buy a Badlands again fyi,
I second the Havalon-I carry a Piranta. I also carry a camp/general purpose knife from Finland called a Metsa (forest) knife. Sharp as a Piranta, but a much thicker blade for big work.
Another thing to think about if you're using binos only, rather than the scope/bino combination: see if you can get an attachment to go on the end of a hiking staff that'll screw onto the front hinge of the binos, and turn `em into a binocular spotting scope. If you're spending long hours glassing, you'll appreciate the stable platform.