Speak to Zarevhi at the Stormspire in Netherstorm. *WARNING!* You can only select one alchemy specialization.
My knowledge of alchemy is vast. It is, however, general in nature. If you wish to specialize, you will have to find others who have narrower fields of study.
If you wish to specialize in transmutation, I would recommend that you seek the help of the ethereal known as Zarevhi. He resides in the Stormspire in Netherstorm.
His mastery of transmutation is... well, outlandish! See what you can learn from him, but beware - ethereals drive a hard bargain.