Elan:
If I chose a manual of golems, would that come with a Golem? There is a gold and time cost to make the golem once you have the manual.
It does not. But we could say that Elan made the golem after procuring the book, depending on what you want it to do. As an added companion for flavor, sure. As an active combatant, less so.
Mara the Blessed:
Question about equipment. Are common magic items considered to be a part of basic equipment? They kinda sit in a limbo, lol. I normally completely ignore them but since there is no attunement restrictions I might be interested in some of them.
Indeed, that's why I didn't mention them in the rarity list. Wouldn't really be concerned about them, to be honest, so feel free to add what interests you (within reason, of course).
Great to see that people are already starting to work on shared background stories :)