Gmail app in conjunction with Microsoft Exchange

Coming over from Android to the iPad; am working my way through the users guide and setting up the syncing. Started with the Gmail app which went fine and I had my email and Calendar but no Contacts. I then followed the further instructions setting up Microsoft Exchange which does Mail, Calendar and Contacts.

Contacts show up when I set the contacts to Exchange or both Exchange/ICloud. I then had two calendars (Google and iCloud). Turned off the iCloud since I want to keep it synced with Google since my phone and computer use that.
So my question is do I turn off the calendar and mail in the Microsoft exchange?

Or what settings should I use to make sure things are synced properly and not dublicated.