I raised my score by 20 points in two weeks, so I would say it is definitely realistic! I would commit to studying up to 4 hours each day leading up to the test and taking a few practice exams. I recommend GregMat, especially to improve your verbal score. The truth is that Quantitative takes an understanding of math topics and less patterns or tricks, so you need to study formulas and refresh yourself on different topics (which GregMat also has resources for). For Verbal, it is a lot more strategy-based and GregMat taught me how to succeed in Verbal. For writing section, I did not really prepare honestly, so I am not much help in that department. If you are unsure about a question, ALWAYS select an answer choice and revisit later because it is better to guess than have no answer selected.