A money log.
That tracks money going in and out of ur characters pockets. The retainers got a log, but the characters doesnt.

Add a simple section to the lodestone(only viewable by you ofc) or ingame in the "Currency" tab.
Where all the transactions show would be really lovely.

Like money spent on repairs, market boards, items from vendors, money in/out from mail, items sold to vendors.

Dont care much about money from market board sales or money from mobs/fates/quests/leves etc.
Just so we can track where the majority of the outbound money goes to.