Any recommendations on things to fill in a handy dandy tomb of stuff. Focussing mostly on trading. But it’s a big book, which needs filling.
Most importantly I would include the list of materials, and any artisan recipes that your group is likely to want.
Easy maths for multiples of various coinage and throne to crown to ring conversions
Related to that perhaps the rituals that buff the resources you use, and which realm if you need to chase a coven to cast them.
In the artisans arms, I saw a very handy “Ready Reckoner”. A large board with conversions of various coinage to equivalent crowns and rings, A copy of that could be helpful.
Maybe keep a log of prices from summit to summit? List of names and groups who do good trades, or people you know have access to certain materials. Maybe a list of bourse holders?
Names of Ambassadors, Nation and Group alongside their Foreign Nations, Ports and the commodities they provide perhaps?