Scored 500 on GMATPrep I - Test on March 3rd. 1

Given your ADD, it may be possible to request special testing conditions. However, putting that aside for now, I think over the next month you have the potential to make a lot of progress, but it's going to be very difficult to get up to 700-level from 500, assuming the 500 wasn't a fluke.

I think to get an idea of how to approach studying, you need to look at your subsection scores.

Below I've listed possible strategies for you given your current quant and verbal scores.

Quant
48+: Your issue is probably timing and getting "tricky" questions wrong. Allocate your time properly (read the question multiple times, don't agonize over not knowing the answer, know when to guess and move on).
43-48: You know most concepts but probably don't know how to approach every single question. Look at your practice tests for the questions that you got wrong and categorize them by question type (geometry, algebra, probability/statistics, counting/number theory, etc.). Tally these question types (in something a lot of GMATClub people call an "error log"). If you took a lot of tests, you should see a pretty clear trend.
35-43: You understand the test but lack an understanding in a good number of the mathematical concepts tested on the GMAT. Work on understanding the concepts and methods in the question types. An error log probably isn't absolutely necessary at this stage, but it'll certainly help. Know your formulas, theorems, and rules for algebra, geometry, probability, statistics, and number theory.
<35: You have probably been away from math for a while and need a refresher on most of the mathematical topics on the exam. Here, I would recommend picking up some math books and problem set books, making sure that you're solid in the fundamentals beforehand.

Verbal
40+: Your issue is probably timing and getting "tricky" questions wrong. Allocate your time properly (read the question multiple times, don't agonize over not knowing the answer, know when to guess and move on).
34-40: You are competent at taking the exam and are familiar with all question types but you probably need to dig a little deeper into the exact questions you're getting wrong (e.g. weaken questions in critical reasoning, global questions in reading comp, parallelism in sentence corrections, etc.). Keep a detailed log of the practice test questions you've gotten wrong. This should help reveal a pattern.
28-34: You are probably having difficulty in one ore more broad question types (reading comp, sentence, correction, critical reasoning). Use the error log and cast a wide net around the kinds of things you want to improve upon. If you have trouble with reading comp, for example, you may want to find prep materials devoted to just the reading comp section and work on that exclusively. The idea here is to make the most out of your time by making the most significant improvements first.
<28: You may be unfamiliar with the test or have difficulty with a good number of concepts. Spend a lot of time reading about the concepts and internalizing examples before going into problem sets.

Hope that helps. The idea is to find out where your most significant weaknesses are (either in concepts or in the way you take the test) in order to figure out how to take the biggest strides from there.