Definitely focus on the general orders, code of conduct, rank and recognition, chain of command, and service songs. A lot of staff has started asking the Navy Hymn cause no one knows it, so either learn it or be prepared to take it as a hit for inspection.
I by no means am an advocate of learning only these however. I say learn it all, if you have the time put in the effort to learn it. If you are looking to do the minimum learn what the leadership traits are, be able to define your favorite and why it is your facorite. Learn your warfare insignia and while at OCS learn your room mates.
As a prior I was asked what mine were, EXW and small craft pin, which are not in the gouge or OCR. For ORLP I wasn't asked much from the gouge since I was a prior. I was asked a lot of odd ball questions such as "who is the commander of a cruiser?" "Who does he report to in a carrier strike group?", "what is the rotation speed of an E2 Hawk eye's rotodome?"
These questions are more designed to test you bearing and response cause you are expected to know the rest.