How to spend time and money most ethically, thoughts?

Here's your subject (if you'd like one): a generic 18 year old male. Perhaps intelligent, creative, and insecure.

In your opinion, what should he do to bring about as much positive change as possible? Study law? Try to assess the deeper roots of poverty and strife? Start a fair treating business hoping to expand and fund his insight?

I think living humbly without excess nor lack is a given. Anyone have experience or knowledge in a healthy low-cost diet meant to suffice? What about reasonable family life? Or having none at all?