Help with combat plz

Just a girl trying to start this game on the explorer mode but I cant figure out how to master combat for the life of me. I’m currently stuck on a goblin king boss battle in act 1 because I definitely entered that fight prematurely and should’ve leveled everyone up higher than level 3. However, since I’m playing in “explorer” mode am I missing a part of the game where there should be more mobs wandering the map to fight and level up? Because I haven’t come across many combat opportunities to level up my team and honestly when I do have a battle I have no idea what I’m doing besides spamming attacks with the highest damage.