My general philosophy is to do some real good in the short run, while learning how to scale that up in the long run -- to the entire planet in maybe 20 years. I'm also very committed to helping people from the bottom up, to give people a break that rarely get one, and to help give a voice to the voiceless.
What is the optimal way to use your money? The answer to that will likely change over time, encouraging effective donors to keep posing - and answering -- questions. But you shouldn't worry. It's like a kind of philanthropy-yoga: regularly asking deep questions about giving helps donors stay flexible as well as strategic.