GMAT Strategy

Hi everybody,

First off all, my English is not very good so please don't mind. Its my third language and in daily life I'm not surrounded with English.

I need to have a gmat score of at least 550. I have a dutch bachelor degree, but I'm not good very good in math and statistics (on scale 1-10, Its doable for my to get a 6 out of 10).
My application to the university has to be completed by november 2013.

I'm thinking to follow a four day course like a month before I'm going to take the test. But I live in the Netherlands and the courses here are all very short. Do you know any good courses in the Netherlands?

Besides that, what is the best way for me to prepare? Which books should I get? There are so many. The course that I'm planning to attend use the Manhattan study guide. Is that well enough to prepare?

How much time do you recommand to study and after which period I should take the test? I'm very nervous that I'm not going to get at least 550, so I would really like to here some concreet tips from you.

Thank you in advance.