How to sync iPhone contacts to Gmail and update them on in-use Android phone

To sync contacts with your Android phone, you need to make sure that you're adding the contacts to your Gmail account on your iPhone rather than to your iCloud account.

1. Turn on Contacts syncing with your Gmail account by going to Settings -> Mail, Contacts and Calendars -> your Gmail account -> turn on Contacts.
2. Turn off Contacts syncing with any other account there.
3. Turn off iCloud contacts syncing by going to Settings -> iCloud -> turn off Contacts.

Now, when you add contacts on your iPhone, they should automatically sync with your Nexus 5X over Google's servers.

Note: If you lose any contacts you added previously on your iPhone, have no fear, they're still accessible at icloud.com and you can export them as a vCard and open up that file on your iPhone to sync them with your phones as well.