I took L3 in 2013, so this advice may be a little dated.
Personally, I spent very little time on GIPS, probably less than 8 hours total. About three of those hours were spent watching Schweser’s instructional videos, another 1-2 hours re-reading the “intro” material, and another 1-2 hours taking practice exams.
I didn’t try to memorize all the tiny detail regarding real estate or private equity valuation. If you try, you’ll just drive yourself crazy. More importantly, there’s only so much disk space in the brain, and if you fill it up with GIPS, you’ll start forgetting other stuff, like Individual IPS.
Just focus on the “big picture”, and some of the introductory stuff. That’s what I did, and it was enough to get at least three of the six questions right on the exam.
Write on the margin what is required and what is recommended for each section. Know the few big dates (1/1/06, 1/1/11) and you will be just fine. It is easier to review when you have all the requirements in one place. Most questions should start with “what is preventing the firm from being compliant” or "the firm is non-compliant because it fails to ". Make sure you know the details about advertisements too as it seems very testable.