Hey Prateek, I wouldn't necessarily bother taking another practice test yet since you have already taken 2 other ones this week. There may be a large difference between the scores of the tests that you have taken so far, but it is clear that you are still a ways from your goal, and even your best score indicates that you are probably lacking an understanding of many fundamental principles.
When I started studying for the GMAT my math was very poor. I would recommend looking into the Foundations of Math book by Manhattan, I found it to be a very good resource for learning all of the basics. I worked through it cover to cover over the course of 3 weeks, and my practice scores improved by 50 points - all in math.
Maybe someone else can give you some advice on verbal, I haven't studied it much because it has always been my strong point. I have heard the powerscore CR
bible is good, as are the MGMAT verbal guides.
My last tip is to stay away from advanced guides right now, such as the Kaplan 800
. There is no point in trying to learn tricks to crack the toughest problems without learning the underlying principles. You'll never see those problems on the real thing without mastering the lower level problem types.
So yes, study basic material, try to learn the fundamental concepts and then take another test in a couple weeks. A 200 point improvement is possible if you study smart and have enough time. If just depends on when you are planning to apply to schools...