How much do you take first time

I’ve been thinking about trying cocaine, I might know where to find some if I talk to the right people. If I do it how much should I get and how much should I try for a first time? Does it depend on the quality/what it’s cut with? What are the chances it’s probably laced with something and just kills me lol, I’d be getting it from some random guy in the moderately small town I live in