I don’t think that anyone knows a clear right answer to your question (at least, I don’t). What is ‘easiest’, I guess, depends on your personal situation. If you have enough money, donating is probably the easiest start. If you are early in your career, maybe read up on 80.000 hours.
See also here for more suggestions: https://www.effectivealtruism.org/get-involved/
I don’t think that anyone knows a clear right answer to your question (at least, I don’t). What is ‘easiest’, I guess, depends on your personal situation. If you have enough money, donating is probably the easiest start. If you are early in your career, maybe read up on 80.000 hours.