Not an expert, just a regular guy, working hard to improve in quant as well.
IMO, I'd say stop using the
gmat club tests in test mode asap. The way I see it, there are plenty of tough quant based tests to use. Manhattan has 6 I think, and Veritas has 7. Then there are the 4 or so offered by GMAC.
Rather, use the gmat club question bank, well, as a question bank. seems like you've taken a few test at this point. Run the analytics. Which question type is showing the most red (assuming you've attempted enough of each question type)? If it's algebra, for instance, go through the errors, stopping at each to determine which question type it is. Lets say for instance you got a linear equation question wrong. read that section of whatever guides you have, and do the associated problem set in the book. then do the associated OG problems for linear equations (hopefully you're guide directs you to those questions). once you've done those, re-try your error. Once you've got it, move to your next error, and repeat. Once you've gone through all your errors, try an algebra quiz with only 500 level questions. If you're not happy with the results, repeat the process. if you are satisfied, try an algebra quiz with 600 level questions. then repeat the error analysis. Do this till you master all the algebra concepts. take a cat from manhattan, veritas etc. find the next week area and continue.
Just takes a lot of time. Also check the post about improving to Q40.