The only way to become the highest overall in NBA Live 18 is to acquire the most skill points that you can. After carefully testing every game mode on NBA Live 18, the fastest way to earn skill points would be playing Live Pick Up Run. Playing The One mode offline does not net you as much xp as if you played online in the pick up games. Typically, the pick up games are much shorter because of a lack of defense. It also feels like less of a grind, compared to the tumultuous task of dealing with the computers shenanigans every game. You could also boost with your friends in private games to really earn skill points fast.