I scored a 680 (Q43, V41) IR 3 in my first attempt back in feb.. I am going to be writing the GMAT again in a few weeks. So far i have not started preparing for the IR. The plan i have is to watch all the videos from manhattan GMAT:
https://www.manhattangmat.com/ir.cfm and use the free qustions from the OG, and the Question pack 1 for practice. I have already practiced with the resources mentioned, but do not remember much so it should be fairly new for me. This should take around 4-5 days total. I am not planning to do anything else. I'm aiming for a 5...I cannot afford to spend more time preparing for IR, as i am way too busy and wish to apply to a few R1's, so have to work on my applications as well. If you score around a 5 you should be ok, quite a large number of your fellow applicants would have taken the gmat w/o IR so the colleges should not hold an average score against you.
"When you want to succeed as bad as you want to breathe, then you'll be successful." - Eric Thomas