@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