Finding such organizations is easier now than ever, since GiveWell has been working on this problem for over a decade: https://www.givewell.org/
And 10% seems like a good amount to give to charity - join the thousands of others already doing it: https://www.givingwhatwecan.org/
The amount of good money can do is tremendous. For example, $3 donated to AMF (Against Malaria Foundation) results in a distribution of an anti-mosquito bednet protecting about 2 people from malaria for 3-4 years (evidence shows: prevents transmission, decreases malaria incidence in the area; kids don't miss school, parents avoid loss of income due to sickness; prevents death, and other good things).
As best as I could tell when I last checked, GiveWell's one metric is life years added/dollar. That's a great goal, to the point where it feels selfish to care about anything else, but when I look at my local community I do also want to know: What charities are most cost-effective at solving the local housing crisis, or preventing the disproportionate number of deaths for <minority group X> in the community, or helping refugees get back on their feet, etc.?