There are two levels to studying for the quant section (or any section!). First, you have to learn the actual material - facts, rules, formulas, etc. Then, you have to learn the GMAT - how they ask these questions and how best to answer them.
It sounds like you've figured out level 1 but not level 2.
Start by taking a look at these two articles:
http://tinyurl.com/executivereasoninghttp://tinyurl.com/2ndlevelofgmatStart a reply to me in which you tell me how what you've been doing so far
does fit with those articles say, as well as what you need to
change in your current approach.
Next, are you using our 5th edition or 6th edition books? I ask because the 6th edition quant books include chapters explaining how to use various strategies to solve GMAT-type questions. We used to teach these pretty much only in our classes but we just added them to our most recent books. (Our classes still teach even more strategies, but the major ones are now in the books.)
From what you describe, it sounds like you need the 6th edition books, but they were only published in Dec 2014...so you may have the older books.
Did you take one of our practice CATs? If so, use the below to analyze (this should take you a minimum of 1 hour):
http://tinyurl.com/analyzeyourcatsBased on all of the articles I've linked, figure out your strengths and weaknesses as well as any ideas you have for what you think you should do. Then come back here and tell us; we'll tell you whether we agree and advise you further. (Note: do share an analysis with us, not just the raw data. Part of getting better is developing your ability to analyze your results - figure out what they mean and what you think you should do about them!)