The amount of storage available on the Moto X 2nd gen. is what it is and that is all there is. Your only choice is to remove unused apps, uninstall updates and disable apps you do not use…(foreign language keyboards and pre-installed apps come to mind), move photos and videos, music to cloud storage or use a OTG (on the go) device, etc.
You mentioned clearing the caches on individual apps, what about the Android System app?. Clearing the Cache
Here is another thread that asks the same question: How do I increase the storage of the Moto X 2nd gen?
Wish I had better options for you.