Which car should be my first?

2003 Audi A4
2007 Hyundai Sonata
2008 Chevrolet Cobalt LS
2006 Volkswagen Jetta
2007 Honda Civic
2008 Hyundai Accent
2006 Ford Taurus SEL

Civic, hands down.

The one that's been the best maintained, cared for and is the most likely to last. That will be more important than who originally built it.

However, if that is equal, I think the Civic and possibly the Taurus would be the most likely to be reliable and have fairly inexpensive maintenance. Again, that's if they've been cared for. A lot of Civics get hack modified, avoid those.

The Hyundais, since they're fairly recent, should be fairly reliable as well. (Remember that Hyundai's 10Year/100K mile warranty is only for the original owner, so you won't get that).

Then there's the Audi and VW. Both are nice cars, and the Audis are usually very well appointed and nice inside, but they can be complicated and expensive. Buying either seems to be a bit of a roulette: some are relatively free of trouble for a long time, while others need constant maintenance. Since you're buying used they should have some history.

And the Cobalt. I don't know much about it, but I've been disappointed with most of the GMs I've seen or driven lately. But I've also never forgiven them after my Olds Cutlass experience (most unreliable car I've owned, by far).