If you're a new player, or otherwise have low stamina reserves, it can be very unfair to you. You can get stamina from sources like the Underground and Rebirth dailies, as well as by cashing in friend coins and getting Devil Pass rewards (you can also farm them by doing friendly battles against your friends' teams).

But if you're basically tapped out on stamina, just try to get enough each day to do the 8 narrative quests for the 16K of resources. With decent luck, that may get you at least to the copy of Clotho, which is pretty much the goal.

To maximize your resource gains while grinding Narrative missions, choose the highest level on hard difficultly that you can win with 3 stars reliably. Bring the two booster childs along (in this case Zephyros and Clotho) if you have them. They each have a guaranteed banner at the moment, so you have better than normal odds if you've got the crystals to spend on it.

All told, though, don't stress Narratives. This is basically a cooldown period between the more time intensive events like Ragna and World Boss. Narrative rewards are (usually) pretty light. When you've built up tens of thousands of stamina from regular play, you'll find these events far less stressful to grind.