Hi JP,
I would start off by taking a diagnostic test so that you can see what your strengths and weaknesses are. I think that you should look for a diagnostic test that gives you complete explanations for each question on the test. Manhattan GMAT has an online test bank that you can purchase for $39. You get access to that test bank that would allow you to take up to 6 tests without repetition. You get complete explanations for every question on their tests. You could also go to princetonreview.com and register on that site. Then, you would have access to 4 online tests for free. I would take a diagnostic test first, before you start your GMAT preparation process because you need to have something concrete to work from. Once you find out what your strengths and weaknesses are from the results of that diagnostic test, you will be able to tell what you need to study the most for the test.
Please let me know how you do on that diagnostic test, if you want to start things that way? Then, I could help you come up with a study plan, too.
What is your target date to take the GMAT?
Greg