Thanks of your interest. it should be possible to beat 4 avianturs or 3 flying scarabs at level 1, I admit it is a lot of risk and there is rng to take into account.
You start the game 1 potion and 1 big potion also with enough gold to sleep at the inn once. it should give enough ressource to learn the enemies spells and then grinding to level 5 I think is the earliest that is possible to beat the boss.