Pimp Andrea and Maria's ride to unlock Alix, Hari, and Leon as customers.
Pimp Alix, Hari, and Leon's ride to unlock Alyana, Jason, and Sandra as customers.
Pimp Alyana, Jason, and Sandra's rides to unlock Jewels, Na, and Zeke as customers.
A lot of the time the kind of things most in need of pimping are body kits, paint jobs, and rims. Go for them first to get a better score.