Thanks for the tips, Starburst98 and Keyen. Looking at the shards system, I can see why it's advantageous to focus on Trisha, Naladia and Elnora. There's also Chharodi but she would be a second earth-element, so I'm assuming it's not worth using her over Trisha who can be upgraded earlier?

As a follow-up question, should equipment just be upgraded when you get it, or is it better to craft?