When fighting enemies such as the Delzweld soldiers, defeat the commanders first. They often carry equipment you can use or sell.
When you fight Cameillia, and afterwards Droguza, find the blue and green boxes on the battle field and break them open before ending the battle. The contents are well worth the effort.
When inside the Flying Castle, do not go directly to the elevators to fight the Divine Ruler. Instead, search each floor for the treasure rooms. There is powerful equipment for every character spread throughout the fortress.