Hey Keesha,
Though it was not the score you were looking for, I applaud you for taking the MCAT twice. Considering you are thinking about taking the test for a third time is even more proof of dedication in my book! I will start by answering your questions flat out. Yes, I think you should strongly consider taking the MCAT a third (and final) time. No, I do not think you should apply this cycle, EXCEPT to a few DO schools (preferably in-state) and any in-state MD schools. In other words, if you have some spare cash and desperately want to test your luck, go for it--but don't waste thousands of dollars applying to 30+ schools. Your chances of getting in, even with "great" extracurriculars, research, leadership roles, and a full-time job are low because of your GPA and MCAT score. I will explain my position.
You listed your cGPA, but not your sGPA, which is more important to med schools. Your cGPA is low for MD schools and okay/good for DO schools. If your sGPA is below your listed cGPA, I do not recommend applying to any MD schools whatsoever--you will likely be wasting your money. If your sGPA is in the range of 3.3-3.5 then consider applying to a few DO schools this cycle--even with your current MCAT, but do not get your hopes up. If you retook the MCAT and scored above 70% percentile (507), you would be in a tremendously better position to apply to schools and may even be competitive for MD, depending on your extracurriculars.
How to prepare:
The MCAT, as you know, is a really tough exam if you do not study for it correctly. Yes, there is absolutely a right and wrong way to study for the MCAT. I am glad you had some improvement over the first time you took the test, that sounds like you are heading in the right direction, though you just have not quite gotten there yet. If you are going to take the MCAT again, invest in a few resources. Either purchase or find Kaplan or Princeton Review textbooks online. Watch free Khan academy videos. Purchase a 3-month subscription to Uworld in your last three months and crank away at passages and REVIEW your incorrect/guessed answers. Purchase ALL of the official AAMC MCAT practice material, including their four full-length exams and all of the question-banks. Once you have those tools, use them in this order:
1) Review content (go through Kaplan books/online notes/Khan videos) (2 months)
2) Begin answering questions on Uworld, or NextStep, or Kaplan's Qbank every day and REVIEW (for the latter month during your review content block)
3) Take one AAMC test per week until your actual test and review every question. Also complete more questions every day than you were previously doing in step 2.
And be sure to read a CARS passage every day: Jack Westin (a website and a person) will email you a daily CARS passage that I strongly suggest you do.
I hope this helps! If you want to discuss this further, just let me know--I am happy to help!
Best,
Jean-Marc