So, one thing I'd like to see is a way to get potions ingredients outside of the seller. Because I've tried a couple times now and I keep getting request for potions that I don't have ingredients for like the protection or dispell potions.
So, maybe give the player all of the ingredients they might need for the first like 10 customers then start introducing requests for potions that the player doesn't necessarily have because they chose not to buy those ingredients or recipes or simply give the player a garden they can plant basic ingredients like thistle or mistletoe or just let buy them at a mark up. Alternatively you could add a come back later option where the player turns them away temporarily and queue up a few different orders for potions they can't make at that moment instead of just refusing the customer