Charming question about CHARM EXP.

I would say that when equipping cash items each item is given a value (quite likely that the more the item cost the more charm it gives) and it gives charm as normal equip give stats and from what spadow wrote "Charm can be increased by equipping/using cash items and when your fame goes up" I guess the true permanent charm is by using cash items (ie: cubes, gach) and by looking at its rewards looks quite likely:
-Increase of a new equip slot (pocket slot)
-Facial expression rewards

But I'm not 100% sure so I might be wrong.