There is one thing you should bear in mind that you want to 9 Dragons Gold become a master of potions, it is better to seek out Lauranna Thar'well in Cenarion Refuge, Zangarmarsh. For the master of elixirs, go to Lorokeem in Shattrath City. At last, Zarevhi, the trainer of master transmutation, resides in Stormspire, Netherstorm.