What would you do if you could Save your life like in a videogame, and then Load if something goes wrong? And what if that ability was the only way to save your universe from ending?
Step through the stage’s curtain; rip off the mask of the wizard who pulls the strings. Close the loop. Hack into God.
It depends on how much detail you want to understand. You can play Steins;Gate and Robotics;Notes on their own, but they are best understood after playing Chaos;Head (personally, I played C;H after them). Chaos;Child necessarily follows Chaos;Head. For Occultic;Nine, you can read it with no prior knowledge, as far as I’ve seen. For Anonymous;Code, you need Steins;Gate at the bare minimum, and at least a decent summary of Chaos;Head’s themes. Anything more is just added references that you’ll be able to get.
Don’t feel threatened and jump in!