You're probably going to hear a lot of advice on this thread.
So, I'll start it off with my 2cents worth.
If it's for deer, any cal. from the .243 on up is good. The most widely used are the .243, .270, .30-30, 30-06, 7mm, .300 mag. (forgive me folks if I left out your favorite)
If you stay with any of the above, you won't have any problem finding a wide array of ammunition at just about any Wally World, or gun shop.
As far as first rifle goes, mine was a remington 7400 30-06 semi-auto. I'm a small guy and I had no problem shooting it from the get go. Recoil wasn't as heavy as I expected and after about 20 shots I was familiar with how it kicked, and got used to the trigger well enough to put the bullet where it was aimed. I think if you're an avg. size individual, any of the above would make a great first rifle. Before going on a hunt, just remember to get a little range time with whatever you choose, and also dry fire it about 30 or 40 times (even more if you'd like) just to get used to the trigger pull.
I just bought the Mossberg ATR 100 in both .270 and 30-06 and both are excellent shooters and only $244.00 at wally world. (It's actually posted in this same group, just look for Mossberg ATR 100) And believe me when I say they are more than adequate for anything you'll ever encounter in the US.
Now about semi and bolt differences.
Like I said my first was the Remmy 7400 semi-auto 30-06. A great gun with a great scope. and at 100yds shoots about 1.5" groups.
My last 2 are the Mossberg ATR Bolt actions in 270 and 30-06. and they both shoot 1.5" groups and better at 100yds.
So to me I'm not proficient enough to notice any differences, if there are any.
But, whichever one you choose, semi or bolt, make sure you get at least 2" grps at 100yds from a rest. Just my opinion but I've always done it that way.
Then do several shots from the standing and kneeling positions to get used to shooting without a rest. This is usually the hardest part, but just dryfire in those positions a few times to get used to your breathing and wobble.
Anyway, good luck and enjoy. Hope this helped.