It is often difficult to know who are the best charities to donate to. An organisation called Effective Altruism has set up a site to try to help with those organisations they have researched to look at who is the most effective in the charitable giving.
Check out the sites below (some are based in Australia (ending in a .com.au) whilst the others are based in USA:
https://www.choice.com.au/shopping/everyday-shopping/charity/buying-guides/donating-to-charity
https://effectivealtruism.org.au/
http://www.news.com.au/finance/economy/australian-economy/stingy-nation-can-money-equal-happiness/news-story/2f54ded2fd2cbe5fd1750aaa75dccb57
http://www.givewell.org/charities/top-charities
https://www.charitynavigator.org/index.cfm?bay=content.view&cpid=2203
https://www.givingwhatwecan.org/