Hey I'm 21 as well.
Gas savers are ok for a little while, but they aren't any fun and where I live people like to run you off the road so I needed something more agressive.
I just sold this 07' toyota yaris ($238 per month):
and picked up this 06' subaru wrx tr ($240 per month), cheaper insurance too believe it or not. Although, more expensive to maintain:
This one has quite a few mods, so the gas mileage is nowhere near as good as the yaris. I drive it like I stole it every day, so a tank of gas doesn't last me very long.