Try Out Different Blades and Keep up Your Equipment
Blades are the central part of Xenoblade 2’s combat system, and each of your characters will have one to pair up with. Of course, Pyra is probably going to be the most useful for Rex, but you absolutely should try out different ones in combat. A while into the game you’ll unlock the Blade option in the menu, where you’ll have the chance to awaken new Blades from Core Crystals. You don’t need to worry too much about using these as you’ll get plenty of Core Crystals in the game, so just awaken them to see what new comrades you might get. As Blades can have wildly different arts and elements, it’s important to continuously try them out to see what might fit your combat style best.
At the same time, you’re also going to want to constantly manage your characters. You can enhance the arts of your main characters, use SP to unlock abilities, equip accessories, and empower characters with pouch items. On top of that you can outfit your Blades with Core Chips, empower them with Aux Cores, and check on their affinity growth. This is a lot to take in for sure, but after working through everything you’ll get the hang of things. Just make sure you’re constantly looking to purchase new items, chips, etc. and trying them out on all of your characters to, again, find whatever fits your style best.