My theory is, if someone has never seen them before, got to be 4,5,6 then 1,2,3, if however they have but didn’t get all of the points (which is what I’m doing for a friend right now) then its 1,2,3,4,5,6..
In terms of preparation for Force Awakens, if you’re not that nerdy then 4,5,6 will do.. If you want the full-on nerd then all of them..