To increase your potion experience faster:

Feasting potions are free. You get bones and make bone powders..LOTS of them. Then you get vegetables and empty vials and make reasoning potions which you take to Mira (WS, 118, 706) and sell for 15 gc and buy feasting potions for 10 gold coins. You can get half as many again potions this way so you endlessly increase your potion skill and number of vials. When you think you have enough vials you can just start keeping the extra 5 gc as profit.

I know you just copy/pasted this but there is a problem. You don't get vials from using feasting potions so basically you are gaining 5gc and trading reason pots for feasting. There is a NPC in melinis that sells Mana potions for 5gcea. This way you can turn in reasoning potions for feasting potions and a vial. OR you could buy Mana potions at Mira for 8gc. This way you only spend 3gc to get a feasty and a vial