Champsing
Why a swordsman? That is so overused and cliche it’s boring. I would prefer the Mc focused on ranged combat since he would have the Monsters to attract aggro when his dungeon is attacked. That way he can snipe from the back with arrows if he becomes an Archer or magic if he becomes a mage. Also a poison master/poisonmancer would be could. He could use the poison to debuff enemies but he could also defend and attack with poison. Maybe take some inspiration from the Impel Down warden with the Poison Devil fruit in One Piece. That would be much cooler than ANOTHER swordsmen MC. On another note maybe have the dungeon evolve to a reptile dungeon so he can have Snakes, lizards, turtles and dragons in the future. He could have cool mosters like Naga, Lamia, Hydra, Gorgon and Orochi.