@sim
In my experience, read the older books whenever you can and follow your interests. Avoid contemporary works unless they're well written popular accounts/fun podcasts. You're better off reading what Caesar actually wrote than some dry academic text.
Try to get a mix of philosophy, history and fiction, including from the modern age. what makes the classics so fascinating is that you can trace their influence throughout history of thought and action. this means you will always have a couple of threads/names to hook pieces of information to.
Emerson and Montaigne are great essayists that carry a sense of scope with them; you can read one of their works in half an or or so and be done with it, but their allusions and stories will draw you on to read more about Alexander the Great, Napoleon or Plato.
Never tried to systemise it but if I did the Trivium would be a central pillar:
https://www.pccs.org/wp-content/uploads/2016/06/LostToolsOfLearning-DorothySayers.pdf
@sim check out my post on Anki in the thread, also MemoryCraft by Lynn Kelly is the best intro into memory palaces I've ever read and I've checked out a few
@sim Anki is a lot less investment up front though
So far, I have been following what interests me and reading as my interests take me. That is the easy part. The hard part is retaining that information that I have read and something that I would like to change. I try to avoid newer stuff because it is harder to find reputable sources for learning the classics without modern sensibilities getting in the way of it.
I have been thinking about reading smaller essays of a work that I have read but I haven't found a place for that yet. Thanks for the tip about the Trivium. Will have to look into that. Makes me wonder how they learned in the past.