3. A Weather-Sealed DSLR Camera
Generally speaking, for various reasons, I still much prefer a DSLR (such as the Nikon D810) over a full-frame mirrorless camera (such as the Sony A7r) for landscape photography. One reason is that certain DSLR models are significantly more rugged and weatherproof than mirrorless (update: this is gradually changing with new mirrorless models).
Eventually you’re going to drop a camera. It happens to all of us (at least that’s what everyone told me the first time I dropped a camera), especially those of us who are out in less than perfect weather conditions. DSLRs made from composite magnesium handle some rough treatment much better than the plastic-bodied entry level DSLRs. My first full-frame DSLR was the Nikon 700. That camera could survive being run over by a small truck. A perfect companion for the clumsy, just-starting-out landscape photographer that I was then.
Also consider investing in a quality raincoat for your lens/camera. I don’t recommend getting one of the cheap, flimsy, clear plastic covers made from recycled sandwich bags…they will tear easily and won’t stay put in windy conditions. Get a cover that is heavy duty… one good coat will last a long time, and they aren’t pricey.
4. A Sturdy Tripod
To handle poor footing out in the muddy, rocky, sandy wilderness, and to protect your camera lens setup, a tripod is one item you don’t want to mess around with. In fact, this is the one item more than any other that I would recommend you consider heading to the northern end of your projected budget in order to select a high quality tripod.
A flimsy tripod could end up costing you a chunk of a paycheck in repair bills. It only takes one good gust of wind to knock over an unstable tripod. Having a nice camera and lens, but an entry-level tripod is like putting four worn down, old tires on a Ferrari. It won’t run properly and it’s dangerous for the rest of the setup.
A good tripod will outlive both of us, so it’s rare you’ll need to invest in more than one over the course of many years. A few extra bucks goes a long way towards getting having a more stable, secure setup.
See Really Right Stuff, Manfrotto, Gitzo, or Feisol for excellent tripods. In my opinion, you should strongly consider carbon fiber over aluminum; they are the lightest and strongest on the market.