The only potions you can buy are Healing Potions from the vendors. The other potions are loot drops, Invocation gifts, made by your Alchemists, or bought from the Auction House.
You should get stacks of the things from loot if you play much.
But if you really like buff potions, consider leveling alchemy. Its fast, you get about 1 level per day (more at the early levels) so you can level it to max in about 2 weeks. It also gives you access to the following which are not found anywhere else:
2 ultra buff potions (I think they combine 2 or 3 of the regular potions, my memory fails but they are pretty nice).
rare recipe: power potions (restore 25% of your AP!)
improved healing potions (act as combined rejuv and healing potions)
also I think you can buy some really good potions with your celestial coins, for those really tough fights.
Or you can try the AH; I think the alchemy made potions are about 2k diamonds each, if you only want a few.
Comments
But if you really like buff potions, consider leveling alchemy. Its fast, you get about 1 level per day (more at the early levels) so you can level it to max in about 2 weeks. It also gives you access to the following which are not found anywhere else:
2 ultra buff potions (I think they combine 2 or 3 of the regular potions, my memory fails but they are pretty nice).
rare recipe: power potions (restore 25% of your AP!)
improved healing potions (act as combined rejuv and healing potions)
also I think you can buy some really good potions with your celestial coins, for those really tough fights.
Or you can try the AH; I think the alchemy made potions are about 2k diamonds each, if you only want a few.