It's very easy to get 300 on the GRE. The average score falls between 150 and 152 per section (and 3.5 for writing). So yeah, 300 is a perfectly average score and you can do much better than that. It includes 8 practice tests, more than 60 online simulations, more than 2500 practice questions and interactive and video-based lessons.
I'm not very good at math, but I used Magoosh for two months and got a 156 (which was better than 64% of people). I would seriously suggest watching all of Magoosh's math videos; I felt like I was finally learning the principles behind the mathematics they taught me in high school. Magoosh's practice problems are also much more difficult. Getting a 300 is easy as long as you put in a little effort (studying, practicing exams, etc.) I'm also terrible at math, but I was able to get a 157 studying a couple of hours every night for about a month.
Getting familiar with the way questions are asked and the concepts being tested in the GRE is very important, so I highly recommend using the Manhattan 5 lb practice problem book to prepare you for the quantitative section of the exam (many concepts to practice and the answers are very detailed). To get a GRE score of 300, you must first make a GRE curriculum. Since you already know your goal score (300), all you need to do is take an official GRE practice test to get your baseline score (that is, the average score falls between 150 and 152 per section (and 3.5 for writing). A total score of 325 or higher should help you gain admission to top universities.
However, even a score higher than 300 is enough for MS. The way you design your GRE preparation decides your performance in each section and you succeed in the test. Even though scoring 320 on GRE is definitely not a finger snap activity, it can be achieved with smart GRE prep courses. Ultimately, however, if a GRE score of 300 is good isn't determined solely by percentiles, you should also know what your specific programs are looking for with respect to GRE scores.