Clear Out All Areas
Whenever you enter a new dungeon, be sure to purchase the area map from the vendor as soon as you hit up the rest area. This gives you an idea of where all the skirmishes and loot chests are in the dungeon. It’s generally wise to try to explore the dungeon very thoroughly before going for the main boss. You’ll get rewards like Phozon Prisms which reward you with new skills, extra potions, and even bigger inventory bags that allow you to carry more stuff.
Some dungeons also contain trial rooms where you’ll get to fight an optional boss to receive an extra special reward. While these are generally a lot tougher than even the main area bosses, it’s always worth attempting them for the rewards. And if you want to avoid these fights, the area map will show you the location, and you’ll be able to avoid the trials accordingly.