Work on what pays the highest and then donate that money to the most effective charity. According to GiveWell.org, that charity is currently the Against Malaria Foundation, which will statistically save a life for every $3500 it receives going forward. It is ridiculously cheap to save a life that would otherwise not be saved. I highly recommend Sam Harris' interview with Will Macaskill on this topic (effective altruism).
http://www.givewell.org/charities/against-malaria-foundation