Upgrade whenever you can - the game reminds you, but improving your offensive and defensive options are valuable and very easy to do in-game. Speak to the character you want to upgrade in your Inner Realm.
Once you discover a bit more about yourself in-game, you'll encounter someone who can help you train. It's hours into the game, so just keep that in mind for when the time comes.
Be sure to check out their official Discord here!
We're creating a list of all the best combos out there and if you'd like to share your findings, reach out to us at [email protected] and we'll make sure to credit them!