I've donated blood and plasma a bunch. Definitely feels good to do good. If you're too poor to give to charity or too busy to volunteer it's a great way to make a difference with a relatively low amount of effort. I know cookies and juice are iconic but in my experience best dono snacks are goldfish
Rugi I don't want to drag this into a political discussion but since you brought it up, I'm curious why you think financial incentives are such a big issue? I think it's notable that (in the US at least) they're completely normal for plasma donations but I think actively banned for blood. I can see the issues but there are certainly upsides too (easy money for some people in need; increased supply of a vital resource). Tradeoffs are real, I don't really have a hard stance here.
Another option many people aren't aware of btw: bone marrow transfusion! It's much harder to find a match for this than blood, so typically a patient will need to search against a database of potential donors. You can register as a donor and get a quick test done to put yourself in the database, and if you end up matching someone down the road, you'll be able to donate for them. The process is more involved than donating blood, but not terribly painful, and you'll be back on your feet in a few days. In exchange you can save the life of someone who probably would have died if not for you, specifically, signing up. There are various charities that handle this but a notable one is DKMS:
https://www.dkms.org/