Combing a root (yellow thing) and a mushroom (red thing) will make an energy potion that fills up a bunch of stamina. Roots also replenish stamina but not as much as energy potions.

Certain events will also replenish stamina, like chilling with the dwarves in the caves.

Maewen or Brindle are probably your best bet if you want to conserve as much stamina as possible. Throkki's animal forms aren't very evasive or defensive and Throkki's whole strategy kind of revolves around getting hurt (which drains stamina with recovery.) Maewen's familiar is a pretty competent fighter so if you're just up against one enemy in the early game you can pretty much let Hazel take care of it and save your stamina.

Hope this helps!