Permanent stat boost potion recipes (Elex 2)

Berserkers, outcasts? Any faction merchants. In general, I would not recommend buying them, they are expensive in crafting and the recipes themselves are easier to find. Especially as you wrote, to start the game. I doubt that at the beginning of the game you can safely kill the trolls. All recipes for har-ki require their heart, and depending on the parameter, a separate troll is required. It's easier to craft eleks for points and use them to raise stats.