It's important to remember that even a small donation can make a difference if it's given to the right charity. For example, it costs roughly $5 for Against Malaria Foundation to supply one bednet that protects two people for 2-3 years. So, even if you can only afford to give a small amount of money, your donation can still have a big impact.
However, the impact can vary wildly depending on where you donate. The best charities can be at least ten times better than a typical charity within the same area, hundreds of times better than poor-performing charities, and the worst charities can do harm.
You can learn more by reading these articles: