Beginner's guide
Best guide around is The Fantastic Manual written by VeloCiryx
Not a guide, but worth reading are Soren Johnson's developer notes on Old World game design.
New player guide by Voqar: https://voqar.github.io/index.html
There is a set of guides linked on the subreddit: https://www.reddit.com/r/OldWorldGame/comments/gh6kfg/list_of_most_guides_of_the_game/
Donblas also wrote up a early game technology guide: Donblas' Early Technology Guide
Questions a player familiar with the Civilization Franchise might face: Questions a civ player might have.