Any reason I shouldn't get the standalone legendary version? I'm a total novice with Steam. I know what it means as a distribution platform, but beyond that, I'm clueless.
I do recommend you get steam, though. It is bar none the best way to get games cheaply for those on a constrained budget, thanks to their biannual huge sales promotions. And there's even a large number of games available for free. At the very least, you should check out Team Fortress 2 (which is free), it'll give you a good introductory idea on how steam "works" while giving you one of the top multiplayer FPSes of all time.