Track the amount, time and kind of potions players in your group use. Keep in mind that you should store the data in a way that it is extendable for more data points in the future. Potions that need to be tracked:

Healing Potion
Mana Potion
Healthstone
Free Action Potion
Nature Resist Potion
Frost Resist Potion
Fire Resist Potion
Arcane Resist Potion
Stoneshield Potion
Living Action Potion
Rage Potion
Goblin Sapper Charge

Implemented tracking for the mentioned Spells used.