wesley's theory - overture/overview
for free - before kendrick was famous. he wants to be famous. has a chip on his shoulder about it.
king kunta - kendrick has made it and is exactly the type of person the girl in for free would want (let's call her "lucy" ;p), hence the easy transition. since lucy is obviously not an actual girl this is where kendrick's relationship with lucy begins.
institutionalized - kendrick realizing that he still has evil inside of him
these walls - kendrick giving in to those evils
u - kendrick reaching rock bottom
alright - kendrick realizing that his relationship with lucy needs to end which also means starting one with god
for sale - kendrick sees through lucy at this point, hence lucy sounding ugly and sort of demonic ("waaannntt youuuuuu"). Kendrick also realizes that he was still immature in some ways after making it, hence sounding really clueless ("where's Ricardo?"). he essentially escaped one evil for another and seems ashamed that at least for a little bit he was smitten with her. we can assume kendrick's relationship with lucy is over at this point and he has once again accepted god.
so from momma on it's basically kendrick realizing that even though his relationship with lucy is over he still had a lot of shit to deal with and then eventually coming to i which serves as the realization of the album. kendrick is also trying to preach this message because in this instance his love interest for the album is someone we can all fall prey too.
(I'm gonna go to bed now haha, let it marinate. the narrative is stronger than gkmc in my opinion, the music plays a larger role. I dig that)