[slackson]

If you want to know enough to donate with confidence, GiveWell has good charity recommendations.

In any case, don't let indecision paralyse you into inaction. Put some proportion of money aside for charity, start doing research, etc. We're not perfect, it's okay to be a bit selfish, and it's good to want to do better. There's any number of options between a spartan life where you donate most of your money, and donating nothing.