RE: best caliber for your first gun
You can't go wrong with any of these:
.270 Winchester
.280 Remington
7mm-08 Remington
.308 Winchester
.30-06 Springfield
I think that the .30-06 is the best all around cartridge, but its easier to find CHEAP ammo with the .308 to practice with. You could really throw a dart at these rifles and be fine with whichever one you came up with.