Okay, so to not make this RP into some sort of mechanic-driven grind fest, we could go with an unlocking system in which after a story event, a set of Personae from your main Arcana (let's say 3 or 4) will be unlocked for purchase in the Velvet Room (you'll determine which Personae will be unlocked and I'll set the prices). After the initial purchase, you can buy them again later for much cheaper. Personae of your other two compatible Arcana can be unlocked by doing certain activities/spending time with certain people? I don't know, what do you guys think? Money can be earned through part-time jobs which will take time away and impede you from doing other things that day. Also, enemies in a dungeon will be pretty strong and if you "lose" a battle, you can choose to either randomly sacrifice one of your Personae to continue the battle or sit out the battle.

So that's basically what I have in mind in regards to earning Personae. Any suggestions and/or additions are welcomed.