It's good to have plans for big charitable actions, but small actions can make a difference too. Even if you give only 100$ or 50$ per year (and 100$ is close to a rounding error on your yearly income), it can still go a long way for some charities. Charities in general need money all the time, and their work is easier if they can rely on a steady flow rather than big sporadic gifts (which require them to invest part of the money they get into fundraising - that's also why small monthly donations are better).
It's also super easy to help, you just need to donate a small amount of cash. You don't have to invest any of your time or to think and plan deeply about it. The advantage of small donations over large donations is that you don't have the same emotional attachment to how well spent your donation is gonna be. (Just investigate briefly which organizations support causes which you care about and look into how well-managed their funds are - usually most of these organizations are pretty transparent, and consistently managed over the years. So you can pick a few favorites and give to them blindly afterwards.)
One big advantage of numerous small donations is also that you can contribute to many causes you are attached to without having to "choose one". As far as I'm concerned, I give to food banks, emergency relief organizations, human & digital rights associations, and environmental protection associations, because I find all these causes to be important.