To achieve a 150 point score increase, you have to learn the GMAT from the ground up. In other words, you wouldn't just do a bunch of random practice questions and hope for results. You would break the GMAT down into topics, such as Number Properties, Exponents, Combinations and Permutations, Geometry, and about a dozen others in quant, and such as Modifiers, Parallel Structure, Assumption, Weaken, RC Inference, and many others in verbal. You would then work on each topic separately to master each topic in turn, by first learning about the topic and then doing dozens, or even hundreds, of practice questions involving that one topic.
Topic by topic prep works super well.
As you do this prep, you would take practice tests, first after a month or two of prep, to gauge how effective what you are doing has been, and, later in your prep, more regularly, to get practice taking the test and see what you have to work on to lock in your score goal.
As you do this work, you may consider using online self-study courses or other resources that would provide the information and practice questions that you need as you go through the process. You can read posts here to see what resources other people have used to hit their score goals.
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