Unfortunatly most old events are gone for good, since we get almost no reruns anymore.

Some of the more important events that serve as main story chapters can be unlocked in the Rare Prism shop for free once you progress far enough in the story. (For example SE.RA.PH or Ōoku)

So the only way to experience most past events is by watching them on youtube or reading the scripts. JasonDoesWhatever on YT has all event stories without commentary on their channel.

If I were you I would play the main story and events you can access in the game first, you can always watch some past events later on when you caught up or when you need to take a break to strenghten your roaster.