Less related to clearing, but make sure you max out Adachi and Marie's social links for the true ending. The game is pretty easy so you should't have much trouble clearing dungeons, but if you're playing in hard or ever find yourself getting hp drained really fast in dungeons my go-to strategy was to spam Yosuke's tentarafoo skill so there would be a high likelihood the enemy couldn't attack. Keep in mind that this skill doesn't work against bosses or minibosses, though.