I’ve got some standing orders of 1 or 2 euros every month for bigger projects like grapheneos and kde. And for small apps that I actively use, I try to donate 5 or 10 euros now and then. It’s not much but I believe if everyone is doing their part we succeed in the long run
5 to 10 bucks here and there for things I use. I do have a couple 5 a month subscription. I could probably give more but I forget