Go with fixing the basics, or at least keep it simple.
Futa potion: The trait is unused. 'For girls who 'want to see how the other side lives'. Adds Futa, Lesbian, Aggressive. Common, infinite, 'good for you'. If the buy system were working, they'd likely be using it a lot.
Anti-futa potion. 'For those who wish to return to normal'. Removes the Futa. The other side effects remain. Same idea here-they'd be buying and using a lot, in combination with the other one.
Ring of the Nymph: 'One can begin to see why the sex trade is so common. These rings allow practically anyone to have the attractiveness and sexual desire of the Nymphs, and the physical strength to follow through.' Adds nymphomania, sexy air, charming, tough, removes fragile. Common, infinite. Imagine a world where everyone, male or female, is packing one or more of these things, and you begin to see how Crossgate is the way it is...
Anti-fear potion. 'Cleanses fear'. Fear -1000. Common, infinite. ...More so when this item's about. No one has any fear of anything, even death. Thus people are both reckless to the point of seeming insanity and very very horny. Girls look at massive tentacle demons and think along the lines of 'Ah, a challenge!' Guys will take incredible risks to get that piece of loot or kill that gang. Add this to the all powerful health potions and...
If the girl doesn't enjoy what they're doing, it's no good to me, so I try to make sure they do.