Have you taken a real GRE Math practice exam (not the Princeton Review one)? You might notice that there are very few abstract algebra and topology questions on the exam. You can leave every single one of them blank and still earn a top score, as long as your performance on the rest of the exam is strong.
My advice: first focus on the areas that you are already familiar with. When you can comfortably answer all of the GRE questions in that area, then - and only then - move on to unknown territory. Don't waste 20 hours studying topology only to add 10 points to your score. Not a good use of your time.
I have not taken a real GRE Mat practice exam. I am about to do that in near future. I think there are about 4 or 5 questions from these two topics in the GRE which is about 30 or 40 grades.
thank you for your advice.