Which are the undeniable Google Play Services permissions?

I just got a new phone (Wileyfox Swift) with Cyanogen 13.0 installed and I am playing a bit with the app permissions. I am trying to understand which permissions can be denied to Google Play Services and which not. After messing up a couple of times with my phone, I think it's a good idea to ask around if anyone has an idea about it... so at least I could avoid to factory reboot once more! :)