Re-take GMAT need some help and recommendations

Hello everyone,
I have had a long unrewarding journey with GMAT so far. Below is a summary of practice tests and official scores. I have gathered the courage to take the test one more time. I would appreciate any feedback on the following topics:

1. There is a huge difference in my practice test scores and official score - are there other students who have faced similar situation? What can I do to reduce this gap?
I do admit I did not give any test with IR and AWA. In the official tests I scored well on both these sections ( IR 6, AWA 5)

2. I am currently using MGMAT strategy guides and official GMAC prep materials. Are there any other
preparation materials or tests that users here would recommend. I want to leave no stone unturned this time.

Thanks a ton for all your help in advance!

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Date Name Score (Quant, Verbal)
March Official GMAT 640 (45,34)

Sept/17 Official GMAT 590 (44,27)

9/21 GMATPrep-3 700(48, 37)
9/24 Knewton_0 660 (45, 37)
9/27 MGMAT_1 650(41,37)
10/1 MGMAT_2 680(46, 37)
10/6 Knewton_1 640 (43,36)
10/9 MGMAT_3 670(45,36)
10/13 Knewton_2 680(47,35)
10/15 GMATPrep-4 690(47,38)
10/16 Knewton_3 660(46,35)
10/18 MGMAT_4 Quant = 46, Verbal - not attempted
10/19 GMAT Focus 46-50 ( this test only gives a range)
10/21 Knewton_4 710(49,38)

10/24 Official GMAT 590 (42,29)