I have shot a rifle, I have never hunted, and I intend to hunt variety of things. I'd like to start with deer and eventually work up to the cougars or bears in my area if they are huntable.
Ok, so I expect then that you don't have any experience reloading either? In that case, you want a rifle with a good variety of off the shelf hunting rounds. Also, will you be walking around in thick brush with shots of 25-100 yards or hunting on open plains with frequent shots over 200 yards? One requires a light agile rifle the other will be much heavier and you may be stationary for half a day or more.
30-06 is still one of the most versatile rounds available, good to 200 yards on most North American game and ammo is easy to find in store. You can also shoot it at a bench for 20+ rounds without getting a sore shoulder or developing a flinch. Suitable ammo can easily be found for everything from accuracy rounds for target, light rounds for deer or heavy rounds with bonded bullets for bear and caribou.
Bears vary immensely in size throughout the continent. With a well placed 30-06 shot and good quality bonded bullet, it will take down any of them (so I'm told) and in fact so will a 30-30 at the right distance. Guides in Alaska tend to go for a 300 Mag, but there aren't many factory light loads for the 300 suitable for deer. I wouldn't want to practice for a few hours every weekend with a 300 Mag. For one my shoulder would hurt and two my wallet would start to complain. I rarely shoot more than 10 rounds of 45-70 when I target practice sitting on a bench, with about 35 ft-lbs of recoil it gets uncomfortable rather quickly. I've seen experienced shooters take the 45-70 and start to shake before pulling the trigger!
When you budget for your rifle, don't forget to factor in a good scope and rings. There's no sense using a $1000 rifle, with $3 rounds with a $150 scope that fogs up and has POI shift at every shot. Often a scope over 10X justifies an adjustable optics (AO) in order to avoid parallax errors at longer ranges, but that's not a good thing to have when shooting at closer ranges as you may not have the time to focus the scope as the deer hops by 30 yards away. So you see, determining what, where and how you'll be hunting is really the first thing you need to consider.
So let's say you go with a 300, and you practice at 50, 100, 200, 300, 400 yards ... you'll also need a good spotting scope, that's another $300-$1000 to factor-in to your budget. Up to 100 yards, you can certainly do without one.
Sounds to me like .50 is probably not the round for you.
Are you buying new or used? There's tons of good used 308's on the market, which will probably cover 98% of what you want to hunt, with decent accuracy up to about 150 yards.
Do you have a mentor or someone you know that's been hunting for a long time? Are you a member of a fish & game club?
Here's my best advise: get a 22LR, get very good at shooting in various positions (bench, prone, standing, kneeling). You can even hunt rabbits and partridge with a 22. Once you're down to a consistent 2 inch group at 100 yards with a scope in all shooting positions, then it will be worth upgrading to a larger centerfire rifle. Otherwise, you're just wasting expensive ammo.
1 shot 30-06 = $2.50
$2.50 = 50 shots of 22 LR
$400-500 will get you a nice used quality 22 and scope.