you don't need potions because its a double battle, she'll heal your pokemon after each fight, and their is usually a relic item to heal your pokemon before you fight -spoiler- and drain the dirty water, circle back around and fill the rooms up with the clean water, another relic, then fight taka and head back to there place and you will get fly after the events, though its not currently useable until episode 16
i'd say stock up on max repels.