At this stage in your career, don't quit a job until you can line another job up. That said, if you can line another up that progresses your career, don't hesitate to quit.

As the old saying goes, you have to look out for #1 (you): no one else is going to in the working world.

While I'm all for moving on and up, though, when your career is just beginning, gaps between jobs don't look great, even if you have a good story for why they exist. Thus, don't leave until you have a new place to go.

And remember another age-old saying: "the grass is always greener..."