In most cases, anything you can disable is ok. Or at the very least, just cause a mild annoyance that is fixed by enabling said app again. So any game, office app, messenger, etc. you won't use can obviously be disabled.
When it comes to system apps, it's a little more tricky. Any core apps required to function won't allow you to disable them, and others I leave unless I have a specific reason to disable them. So far, I only disable a few system apps:
Mobile Services Manager (formerly DT Ignite) and AppFlash: These allow carriers to install additional bloat after the initial setup.
com.android.providers.partnerbookmarks: I disable this, along with making a couple changes with Chrome flags to remove the spam at the bottom of the new tab page.