I'm not really sure how to write a guide for this because it's pretty straight forward.
However, I will say this: If you can find a street challenge that is very quick and easy to do, you can make enough money to get this pretty quickly. I use Cepheus St. 1 for this. It will only net you 1200 per run, but it takes about 90 seconds to get though it, including front and back load times. Given the varied cost of the outfits, it's about 60 times if you don't spend the money on club challenges.