Montana has lots of variables in terrain. Save the money, drive it, and the jeep will let you know if it needs anything other than gas.
Buy a jeep cover for bad weather and take the top and doors off.
I bought this cover because it is inexpensive and seems to get the job done. This one fits sloppy, but it is easy to throw on and off. https://www.amazon.com/gp/product/B07P7S2S7Y/?tag=jkforum-20
If you let a dog ride you need something to protect the seats.
If you don't have a trailer hitch the $50 kit on amazon is excellent quality.
I agree. Save your money and drive it. Over time, you'll identify things you want to change or repair, and can either fund from what you've saved or continue saving until you can. I know it's difficult when you're anxious to customize your vehicle!!
My advice for jeeping on a budget: don't get tempted by cheap stuff! You really shouldn't skimp on most things, so make a dream list and save for it.
Stock jeeps can do a lot more than you think so don't be afraid to get out there before you mod!
You can also find a ton of sources of what to buy first here on the forums or on the internet- I think TrailRecon has a couple really good videos about it.
------Safety and recovery are priority-------