>>724757179
You need the battle chips to level up your characters. And every 10 levels you need a couple of books to promote your characters.
Chips you will get an insane fucking amount just by playing and doing the story and whatnot. Maybe you'll get some books too. But beyond that to get both you mostly need to do the simulations (which is using aether to farm mobs and get rewards, yes)
Going into chaos gives you loot (you have 4 tickets to retrieve loot after finishing an expedition, they replenish each weeK), and you can save the builds of your characters (their equipment and decks). These builds you take to the story, and to the simulations (to complete challenges and get more rewards).
It takes time to get your teams going, yes. I've been playing a lot and have six characters at level 40, and now working on the next 3.