Where should i buy my car insuarance?

Ok, first of all, i live alone now, i'm 20, my dad left me here in california alone, i got my license and i want to buy a second hand car from someone i know, so my question is, where should i get my first auto insuarance?, i can pay $2000 for a second hand car, and i can only pay $100 a month for a car insuarance. Any tips guys? I don't know anything about car and insuarance, and nobody here cant help me here. Plz help advice will b helpful too. And what kind of car to buy? Thanks.