I'm not sure whether you have actually prepared for the GMAT once or not because you have said that you have wasted many hours and at the same time you are saying that you are a beginner.
I'm assuming that you're talking about starting afresh and you're not in a hurry to take the exam within one or two months.
The first step you may wanna take is research more about this exam- what does it test,how much time do people usually devote who end up getting 700+, what are the best resources/books, what is the best strategy, and things like that.

After you have done that for a couple of days and got ten a good overview of the exam and as a result have gotten into the "GMAT mode" you may wanna kick off your preparation.Start with a Diagnostic test. to assess your current competency level.This will also enable you to get a first hand feel of the overall exam. Analyze the test and you'll get an idea about the areas you are good in and the areas you'll need to really work on.
Remember that for scoring 650+, you'll need to really good with your concepts and you need to make sure that you are sufficiently prepared to take on each of the areas. For tackling each areas say SC,CR or RC in Verbal or similarly in Maths, you may wanna get books which will enable you to master these areas well.
Keep participating here on the forums-I believe that this is the BEST way to improve as the community here will keep you steering in the right direction.
Hope that helps!