My top priority when it comes to a first car would be reliability. Do not waste your money on something with really high miles and a bunch of defects. Buy off craigslist. Be smart about it and don't jump the gun. Consider your decisions very carefully. Be very careful for scammers and cheaters and you could probably get a pretty nice car for a low price.
After reliability I would go for performance and fuel economy. Then I'd narrow it down to a manual transmission because they're just better, but only if it has a sufficient amount of horsepower to make a manual actually enjoyable.
I don't really go for a specific brand. I'd drive almost any BMW, Porsche, most Fords, or something with a decent 0-60 (around 6-7 seconds). It's not like I plan to floor it at every stoplight, I'd just like to have a little more power than the average Japanese commuter sedans that have my school parking lot under siege. I like convertibles. Mainly roadsters because they're easy to park and most are lightweight. I want to escape driving a full-sized everywhere as I do now