My recommendation is to get a tutor. If you live near a university, try finding a grad student who tutors on the side. They tend to charge very affordable rates.
I have been working with a tutor for 6 weeks and my learning curve has shortened dramatically compared to preparing on my own. For example, I used to struggle with exponents. However, in reality, I was only making one type of error in my logic. My tutor was able to see this immediately, show me how to correct my logic, and now exponents are one of my strongest areas.
What I did was purchase the Kaplan math workout, and hire a tutor to work through it with me. I know that is heresy to this board, but I think Kaplan is great for learning the basics. Learning the basics is essential. Speed will come with time, which is why it's good you're starting now. Unless you're a natural test taker, or have a strong quant background, the GMAT isn't something you can cram for. Plan on giving it some time to prepare for. I recommend giving yourself 6 months at least (this all depends on the score you're aiming for). To learn the subtleties of the way the GMAT words the questions you will want to work though the official materials and perhaps consider supplementing with
Manhattan GMAT guides. But the Kaplan guide will ingrain the basics in you. What I've found is most of the test prep guides have good questions that will help you learn the basics, but often do a less than quality job in explaining the answers to the questions. I personally believe they do that on purpose so you take their courses. Rather than take a course that goes at a set pace, invest in getting the one-on-one attention of a tutor. It will pay off enormously.