I took the GMAT twice without really studying and scored a 500 and 480. TERRIBLE! Then I took the MGMAT Prep class and scored a 590. Still not good enough! I really need a 650+ and want to know how bad it looks if I take the exam again.

What do you think?

The majority of schools take your highest score. It doesn't look bad to take the test again. If you're aiming for Top 20 schools, it really is a not even a debatable point. You need to take the test again.

I think most schools start to get concerned on the 5th or 6th try, so you have at least two more tries before you need to get worried (but it is December)

Good luck!