Well, let me start by saying, I am fully aware that 720 is a great score and I have used it to apply to top 10 schools and have interviews with them.
But from the initial 700, I just thought two more tries from that point I would have made 740. But needless to say, I'm happy with it and would not have ever gotten here without this forum. So even though I'm extremely late in sharing my experience I hope it helps someone even just a little.

Nearly 2 years ago I decided that maybe I'll want to do an MBA. I did some research and realized my GPA was outside the 80th percentile of every top school.
Yes, I had some legit explanations and I'd say I have a strong application except my for GPA. So I knew I had to blow my GMAT out of the park for a top 10 school. And I also felt I needed to prove my brains to MYSELF. Given my 2.87 GPA, I just KNOW that I'm so much more than that number.

Early days
Did my first mock on GMATPrep. 550! (I dont remember exact breakdown but V was better than Q)
My jaw dropped to the ground! Sure I had a bad GPA, but I was in an engineering major! How could I have done so bad in Quant?
Mind you, at that time I didn't have THAT big a sense of urgency. I was 25 and my career was going just fine so it was still in the "eh sometime in the future" basket.
I did some research and saw the price of GMATPill and saw the reviews and bought it - what a waste!
I'm sure it has some merits, but it totally didn't work for me. I hated how in the videos there were often small spelling mistakes and attempt-yourself questions would have the answers highlighted straight away (so you attempted it already knowing the answer). I dont know, I'm sure to some people this source had merit, but I would never ever recommend it. I used this to study maybe 3 hours a week for 3 weeks, then stopped all together.

Then I decided: okay, I'll go with the old faithful that everyone talks about - Manhattan GMAT Strategy Guides.

Serious Study
The MGMAT books arrived and sat there for about 7 months before I opened one up (work got busy, blah blah blah, excuses excuses)
It suddenly clicked for me that if I wanted to make rd 1 apps for 2016 admission, I better get going!
I realised that doing a bit here and there was never going to work, it was all or nothing.
So I did. I had a vague 2 month plan - it's pretty simple with MGMAT, the books are numbered 1-9.
I decided to cancel whatever weekend parties I had, or limit it to fewer hours.
And the key was really doing a little bit each day. 30min a day is better than nothing! ONE question a day is better than nothing.
DO NOT cram it all in one day on the weekend, your brain wont absorb it.

I also booked my exam. DO IT! It'll give up a deadline.

I went through each of the quant books in 1 to 1.5 weeks each(I didnt use the OG yet - I probably should have)
I did a practice exam every 2 weeks.
And here were the results
CAT1 590 Q37, V34
CAT2 630 Q42 V34 (was super stocked the quant study was paying off)
CAT3 620 Q39 V36 (didnt know what happened, was feeling pretty dejected, but read that slight variances are normal)
CAT4 590 Q39 V32 (I nearly fainted! at this stage I'd just finished all the quant books and started on the OG)

I did CAT4 on saturday morning. I started frantically searching forums and read that MGMAT quant is harder and the only real predictor is GMATprep. But at that stage I really was about to give up, thinking I'm actually exactly what my GPA says I am.
So guess what, that night (yes after the MGMAT CAT) I decided to take GMATprep. whalla 680! Q47 V36 (W-T-F, excuse my french, but that's ridiculous!)
The quant as SOOO much easier. They were do-able in 2min.

After that, I decided to take MGMAT CAT results with a grain of salt (sorry, bucket of salt)

I continued on, doing MGMAT verbal books and doing my MGMAT CATs. I was pretty confident with verbal especially CR, I felt it was just logic. SC was my weak point. I'm not into grammar. I barely knew what MGMAT was trying to say with all the participles, helping verb, auxillary verb etc.
CAT5 690 Q42 V41 ( I was confused, this actually seemed close to the Gmatprep composite score. BUt quant was still waaay too low)
CAT6 640 Q41 V36 (Ok i know i said take it with a bucket of salt, but given how accurate people have said MGAT CATs are, I was getting a bit worried)

I soldiered on, started doing OG Questions and reviewing them.
I re-did the last 30 questions of DS and PS
I bought Magoosh as it was on special. I loved its quant practice questions.
Magoosh was simple but clean and decent UI. GMATpill was not.

Uninstalled and reinstalled GMATPRep and did the first exam again (i had forgotten the questions in this exam that I did a year ago so it was predictive)
GMATPRep: 700 Q47 V38

I bought the GMATPrep exam pack
GMATPREP Exam pack 1: 700 Q48 V38

GMAT EXAM 1
I read and memorized a template for the essay, reviewed IR questions from my GMATPrep.
I did my research, knew mostly what to expect. EXCEPT! I underestimated the time it took to sign-out, bathroom, food, water, sign back in.
Essay - used same format as the one i read the night before
IR - Reviewing GMATPRep was all i did
Quant - I RUSHED through it. It was stupid, but I guess I was still trained from MGMAT CATs to just GO GO GO. I had about 18min for the last 5 questions. Took my time with one of them because i couldnt solve it. Ended up still rushing the very last question
Went to break and took a min longer!
Verbal - so with the min lost I was a bit shaken in the beginning. But finished on time without too much trouble.

Result: IR3(woops), 700 Q48, V38. Essay was 5.5.
It was exactly in line with expectation but I knew it was still at the low end of the schools I wanted. I got home and started talking to a lot of admission consultants and basically all said with my GPA, 720 GMAT would go a loooong way.

I decided if I'm paying 200K (fees +living expenses abroad) I better go to a top 15 school! So that day, after my 700, I decided on a retake.
My friend from interstate came and I didnt do any study during that time

GMAT EXAM 2
I bought GMAC's new score breakdown thing and saw my quant breakdowns were even and my verbal was
SC:46th percentile
RC:92nd percentile
CR:96th percentile.

Boy was that a revelation! My SC is what has kept me at V38. So naively, I thought, ALL that I need to do is improve SC and I'd be at V40 and get my 720.
I booked my exam for 1 month's time. Yeap, a month, four weeks, just to study SC , this should be easy.

I decided to use magoosh's sc videos. They had about 10 videos just introducing each grammar term. I was a studious student and revised everything from the beginning :verbs, gerrunds, participles you name it. I review MGMAT SC book (it's very similar to magoosh). I did feel aimless when i studied these and the results weren't showing. I still wouldnt be able to pick the right answer. If anything, it made me worse. As a native speaker I knew how it should SOUND, but I decided not to let my ear stray my grammar.

GMATPREP exam pack 2: 700 same breakdown. I was getting worried.
I re-did a GMATprep and got 710 (with a few repeat questions).

I did my second exam, 100% wishful thinking that i'd get 720 but deep down not believe in it. I was sooo nervous.
So nervous that i lost my time track for quant.
For verbal, I started not being able too easily see a clear answer for CR (my forte!)
I knew it was a disaster...I ran out of time for verbal and guessed the last 4 questions.

The score popped up 680. I didnt even remember the breakdown, i was so panicked i just clicked "Cancel score". (they just introduced not reporting this).

Post mortem:
1. I cannot naively think just improving sc will boost my score, GMAT is holistic, even if i think im good at other areas, i need to review them
2. I need to do more mocks to get my timing right. Stress does strange things to peoples brains under pressure
3. I did not study SC correctly, GMAT is a test of logic, not grammar. I'm not getting a journalism degree.

I was more motivated than even to do the exam again (which means i'd miss out on R1 applications)

Exam 3
-I did more research and did some trial with e-gmat and loved it. I found the accent a bit annoying (this isnt racist, i'm ethnically asian, I just was not use to an Indian accent, my fault really because the course is brilliant). I bought the SC course. It was cheap and more importantly SO SO SO SO logical. Not a single word of gerrund or whatever was mentioned. I cannot recommend this course enough. It sells itself short my marketing only to non-natives.

I made sure i reviewed Quant and a bit of CR and RC.
Even gave GMATpill another chance - still hated it
Tried a few mocks from other companies
Veritas offered its exams for free if i submitted my gmat score to them - they were just as abnormally hard as MGMAT
Economist - thought it was pretty good

So 3 weeks from my last exam, i felt ready this time.
Walked in, took my time with the first 10 questions of quant. Played the rest of the timing perfectly.
Verbal, well I couldnt tell if i was doing well or not (SC still annoys me). But I was calm and much more confident in my answers. I reminded myself not to dwell on any question.

Results: 720 Q49 V39 (I think some people have gotten 730 with this breakdown? but meh whatever, I wasnt ecstatic but I felt dignified).

Overall
-Serious study all up was 4.5 months (If I knew the pros and cons of each material then, it would have probably been less)
-I think my studying strategy for my 2nd GMAT was completely wrong! The moral of the story is DO NOT focus too much on grammar for SC. GMAT is ultimately a test of logic
-MGMAT is great great study material, just SC was too grammar focused. Their mocks were too hard on quant
-e-GMAT is GREAT for SC. It's marketed for non-natives, but honestly, it is just a LOGICAL way of looking at SC. MGMAT and Magoosh got a bit carried away with the grammar and grammatical terms.
-Magoosh is good for Quant. The SC was again, waaay too grammar focused, even more so than Manhattan.
-Not CAT even comes CLOSE to being as predictive and realistic as GMATPrep

And my parting words: What got me through was my belief in the end goal. And that belief wavered a few times throughout the course of my GMAT study but I snapped out of it. If I can start at 550 and get to 720, you can too. Oh and I have a 2.87 GPA and got interview invites to Cornell, Stern and Columbia. I just submitted Yale and UCLA and am awaiting their results.

hi congrats on the great score! Good luck with apps!

can u expand a bit more in what way magoosh is good in quant? i am thinking to may be to take some affordable quant course thx

Overall, Magoosh closely follows Manhattan GMAT. In fact a lot of their study plans even have the option for you to combine studying MGMAT strategy guides with magoosh.

Pros:
*Great question bank (and you don't have to do questions one by one, you can for example select 10 to do under exam conditions, or do one by one. You can also customise by topic). It gives you a lot of flexibility. Mostly good explanations, if some weren't clear I just searched it on GMATCLUB, usually someone here will already have your question.
*Great videos which are short and in bite size portions
* Videos just make it less boring as compared to reading book.
*I believe content is quite comprehensive. Though I didn't go through all videos, only areas I was weak on. I can say their combinations and permutations were done really well. The other areas I used were good too, but I had the benefit of reading all MGMAT guides beforehand.

Cons:
*Content, though comprehensive, might not be AS comprehensive as MGMAT guides. I'd say Magoosh is still a more add-on to MGMAT rather than stand-alone product if your quant isnt strong.