Any tips on preparing Gmat

Target Test prep will get you where you need to go for Quant. Their Verbal is okay, but still worth going through. I found that the best thing with Verbal is to do a lot yourself using GMAT club, and then go use their error tracker and analyze your weakness. After that, do the weak things. Once you've done that, go to GMAT Ninja on Youtube and watch al his stuff, and copy the methodology religiously. Manhattan is good for sentence correction as well.

The GMAT really is about getting a wide range of topics down, and then going deep enough on each so that you know what to do when you see it. Train your methodology so that you start attacking each problem correctly FIRST, and then go into harder things after that. Get your "perfect" down pat when you see a sentence correction (e.g., check for your subject verb, then parallelism, then pronouns, etc.) and mark things off. Same thing with Quant, be able to recognize when it's combinatorics or rates or whatever, and then have your framework of how to deal with each type of problem.

Verbal, you'll want to be sure to mark off everything that is WRONG before getting to what is right. Quant, don't do that.