What kind of routes are you trying to climb (at the crag and in the mountains)? Keep in mind you'll replace a rope after a couple years of hard use, so forget those dream goals and only consider what you'll do in the immediate future.
Second, is age/fitness or budget more of a constraint? When I started doing alpine routes I was working a shit job part time, but I was 24 and an ex-collegiate distance runner. I got one fat rope and took it on everything and it worked fine.
Simplicity will force you to adapt and think creatively. My advice, spend the extra money on gas, go climb more with a cheap rope and the mountains will let you know when the extra skinny line is worth it.