Be sure to use an email address you check regularly and intend to keep indefinitely. It will be used for billing and all communications about your Google Fiber service.
You need a Google Account when you sign up for Google Fiber. If you have a Gmail address, you already have a Google Account and can use that account when you sign up.
If you don't have a Google Account, you can create one during the sign-up process using either an existing email address from another provider or by creating a new Gmail address. When you use an email address other than Gmail, you'll need to associate that email with your Google Account if you haven't already done so during the sign-up process.
Don't use a Gmail address that's managed by a third party (such as your employer). If the only email address you have is managed by a third party, you can sign up for your own Gmail account during the sign-up process.
If you still have any questions about which email address to use, contact Google Fiber customer support.