So it seems like activity points is summary of everything mentioned - reading, reacting, commenting? And reading points is something unexplained, looks like you need co leave comments on threads
Seems a bit nebulous but that's like the section I have the most points from just scrolling through and reading threads and occasionally commenting. I don't really rush to zoom through pages or anything idk but the score goes up pretty consistently just chilling and reading comments.
My reading score is just going up naturally by reading threads and interacting with the community. I don't spend a crazy amount of time doing it either. Just hang around and talk to people and you'll get there.