What's the Practicum in Advance Alchemy quest reward?

I think you get some alchemy ingredients as a reward, but that is actually not the important part. After finishing the quest you can buy alchemy recipes from him, which is far more important. The improved and superior versions of potions and bombs are very powerful, access to more recipes is the actual reward.

The reward for this quest, according to the GosuNoob database, is:

• 5x Sulfur
• 5x Alcohest
• 5x Han Fiber
• 5x Saltpetre

This will probably be in your alchemy tab in your inventory - but as you've likely already got at least one of each of those, it might not have been immediately obvious.

In addition, as mentioned by Mad Scientist, it unlocks Gremist as an alchemy vendor, which is important if you have any use for oils/potions/bombs.