640 is not dismal! Yes, there are higher scores, but 640 is a very respectable score.
We don't do any kind of admissions consulting; our area of expertise is the test. If you would like to get some advice on schools, you can ask some admissions consultants (we have a folder here called Ask An Admissions Consultant).
But just a note: do some research of your own first.
The schools all post their data - but test scores are only one factor in making this kind of decision - and they're not even the biggest factor. (Nobody could tell you what your chances are at any particular school based on test scores alone.)
You need to think about whether you want to specialize in anything, or be in a particular geographic area, etc. Start looking at the websites of any schools you have heard about. You might also want to invest in a subscription to US News & World Report, which ranks the top b-schools in the world and provides lots of data and information about them.
Have you seen this article about developing a study plan?
https://www.manhattanprep.com/gmat/blog ... our-score/It's a good place to start. As you develop your plan, feel free to run it by us - we'll tell you whether we agree or disagree.
If you would like, we also do have programs that provide complete study plans and resources for you - such as our self-study programs or our classes. If that sounds of interest, take a look at our website for details.
Good luck - check back in and let us know how it's going!