I think you need level 2+ to make poison potions from white/grey mushrooms or rotting food. I believe the alchemist and Tingalf in Ars Magicana (east and north of the barracks) consistently have poison.
ALCHEMY SPOILER THREAD

Frost on a weapon ignores the monster's resistance, so it will work on things Freeze does not effect.

Otho can repair items, otherwise there is a blacksmith in Ars Magicana.

Bow Expertise. I believe True Shot is still broke.

Unless you use a lot of magic, I would stop putting points into intelligence, and rely on item bonuses or charms for mana. As a warrior, I completed a game with intelligence 10, mana 574.