If you've never hunted and have never (or rarely) fired a rifle, then you might want to consider minimizing recoil and muzzle effects. To do that in a "deer rifle," while still maintaining acceptable accuracy and deer-killing power, I'd go with the lower-powered 25's and 26's, the .257 Roberts, the 250 Savage, the .260 Remington, and the 6.5X55. In that range you have all the deer capability you need while minimizing muzzle blast and recoil. The higher power cartridges are fine performers, but aren't any more accurate than the ones I mentioned, won't kill deer any deader, and aren't quite as pleasant to shoot.
The .243 (and 6 MM Remington) are usually fine performers - accurate, low recoil. People whom I trust, however, speak of occasional failures that might be attributable to insufficent bullet weight or jacket thickness, when shooting deer. OTOH, others, such as Art Eatman, have had no such failures. Buying a new rifle, however, allows you to avoid this potential pitfall.
Writer John Barsness speaks of the 6.5X55 as the best-balanced, all around cartridge available, easily capable of taking elk, as well as being ideal for deer. I bought one (an inexpensive Ruger M77 MkII) and find that I enjoy shooting it very much, and do so 25 - 50 times at each range session, a much higher number than I was capable of shooting with previous cartridges. As this is an extremely poular cartridge in Europe, you run no appreciable risk of ending up with an orphan.
This is really a fine cartridge when handloaded, but is very adequate for deer in its (extremely) mild factory loading. The cartridge isn't rare and can be found at most large gun stores, but you wouldn't necessarily find it at smaller stores and gas stations where you'd find only 30-30, .270, and .30-06. Just buy enough when you find it and don't leave it on the kitchen table when you go hunting and you'll be fine.
Jaywalker