Once you have covered all the basic concepts, I would recommend you to take two practice sets. The first practice test is taken from the Official Guide to GRE and is labeled Practice Test#1 and starts on page 327 of the guide. Consider the paper test to be a warm up for the computer based GRE test. After taking the test, you can review my video explanations to any of the questions that you may have missed.
Take the POWERPREP Online Test 1 as your second practice test. The POWERPREP test is available for free from ETS’s website. This computer based test is section adaptive, meaning the difficulty level of the second quantitative reasoning section will depend on how well you did on the first quantitative reasoning section. Also, the POWERPREP test comes closest to the real GRE test and the results from this first test will give you a solid initial baseline. You can review my video explanations to all of the quantitative reasoning questions in this test.