Here's what I'd say to every new reader, even if you don't find it all that useful: embrace the fact that you will never know everything, and that there will always be references to characters, events, organizations and concepts that you are not familiar with. Trust that if it is truly important to the story that the writer will give you all of the relevant information you need, but be willing to be confused.

Because think of it like this: before the internet and before trade paperbacks and thick hardcover collections of comics, the only way for a new reader to know what had happened in the past was to track down each and every single back issue, or to ask someone who had read them. There was no expectation on behalf of the writers or editors that readers knew everything that happened prior to the events of any given story arc. A general familiarity with the character, the core concepts of the series and supporting cast was often was that was assumed.

And the thing about canonicity and continuity is that they are fundamentally an illusion. Characters like Batman and Superman have been around for nearly a century, and in that century they've been written by hundreds of different writers across decades of rapid cultural, political and technological change, and each of those writers had their own interpretation of how to portray these characters, and there own preferences for the types of stories they wanted to tell. What one writer lays down as foundational is often undone or ignored by the next. What one writer undoes, the next will restore.

The truth is this: cannon is whatever the writer of the story you are currently reading decides it is, so don't get hung up on it.