GMAT Strategy

60 point increase is completely achievable in a month, provided you devote several hours a day to verbal and math. I tutor only math and have seen 15 percentile jumps in my students in a month, working only on the math.

It's a good idea to read the MGMAT advanced sections because just a few more problems answered correctly will give you the desired score.

For overlapping sets, I would suggest work with a good tutor. I improve this topic in a week, with a two hour session covering the correct approach (venn diagrams, tables and when to use which), a homework of 100 problems close in style to the official ones, PS and DS, and a two hour post-session to show the correct solution of some homework problems. A good tutor should do something along these lines.

For algebra, you should practice with algebra book, factoring and foiling expressions, using factoring to solve equations, solving systems of equations and knowing when the problem has a single solution for DS.

You should practice more problems overall, UNDER TIMED CONDITIONS. I would suggest the Princeton Review 1037 GMAT problems book because these are close to the official problems in style. You should also practice regularly CAT's: GMATClub, GMATPrep, GMATFocus and LEARN from each mistake you make. Mark problems in which you make silly mistakes that you could have avoided and compile a 'super-set' that you re-solve a few times to decrease the probability you make such type of mistakes in the future.