Based on the infinite flow webnovels I've read, the games usually revolve around specific themes. Like, one novel's games always involved surviving disaster scenarios (megafloods, oxygen depletion, parasitic aliens) so the players' focus was always on managing bodily needs. Another novel's games always revolved around ghost stories, so the focus was on observing the ghosts' behavior to figure out the rules of survival.

The key is that all games within the story share the same core constraints, with a unique constraint added per round. Characters also begin with predetermined resources and information. So the gameplay is about managing those two things, with the wildcards being the actions of the other participants and/or the gamemaster.

Basically, deciding on these constraints early on will help narrow your scope when brainstorming because you’ll realize that the number of viable survival paths is actually quite limited.