GMAT Strategy

Hi there,
I would appreciate if you someone could recommend good GMAT practice tests (besides MGMAT and Official ones) and strategy to improve my scores
I took the 1st Official test prep without any studying to set a benchmark. I got 680 (49 q, 33 v).
I realized that my sc is my greatest weakness and used MGMAT 3rd edition SC guide for a while (I bought the 4th edition recently and realized that 4th edition is far better). I also used Kaplan 800 which was mostly useless and GMAT OG (12th edition). I did not practice RC or CR questions as I was doing ok on those questions.
Below is the summary of scores. I took my first GMAT in end of August and got 620 (49 quant, 27 verbal) which is below well below expectations. Then I decided to take a break (took a trip to Europe) and came back and pushed hard again. I got 700 in MGMAT and 690 in Official Tests 2 days before the exam.
On Saturday, I took GMAT for the 2nd time after a month break and did worse. I got 610 (42 quant, 33 verbal).
Any suggestions would be great?
Thank you.

Official GMAT Test Prep (before any studying)
Quantitative 49
Verbal 33
Total 680
MGMAT1 Quantitative 45
Verbal 36
Total 670

MGMAT2 Quantitative 44
Verbal 32
Total 630

MGMAT3 Quantitative 44
Verbal 26
Total 580

MGMAT4 Quantitative 47
Verbal 31
Total 640

MGMAT5 Quantitative 47
Verbal 34
Total 670

MGMAT6 Quantitative 45
Verbal 35
Total 660

MGMAT7 (repeat) Quantitative 47
Verbal 38
Total 700

Official GMAT Test Prep 2 Quantitative 49
(after 2 month of studying) Verbal 34
Total 680

Official GMAT Test Prep 2 Quantitative 48
(repeat) Verbal 38
Total 700

Verbal appears to be your critical vulnerability. It's the opposite for me.

Did you analyze the questions of missed on your CATs for trends? Karl Von Clausewitz states in "On War": Avoid surfaces and strike at gaps. If you're fairly happy with your quantitative abilities, don't even waste your time reviewing quant. Shore up your verbal aggressively and relentlessly.

SC was brutal for me as well, but that was before I knew that phrases had to be congruent in "parallelism". The Manhattan Guide was very useful to me as well.

Sorry if my GMAT approach is a little bit "caveman-ish", but it seems to be working well for me...