At the moment, the Xenoblade Chronicles 2 Expansion Pass doesn't have enough major content to be called a meaningful one. You're not missing out on anything substantial from not getting the expansion. Luckily, the more interesting contents such as new BLADEs, Challenge Mode and even a brand new story are promised to be released in coming months. I recommend that you wait and see what those promised contents would bring to the table first, before picking up this expansion pass.
* Passion of the Artisan (available from chapter 2)
* M.I.A. Nopon (available from chapter 3)
* Industrial Sort of Tour (available from chapter 5)
* Midnight Feasting (available from chapter 7)
* The Lone Watchman (available from chapter 10)
* Driver Essentials Set 2: 10 x Rare Core Crystal, 1 x Legendary Co...