If you have a Gmail account, then you have a Google account. Just click subscribe on the channel you want to subscribe to and also click the bell icon to get notifications about new uploads from that channel. If you aren't already signed into Google, obviously it will prompt you to sign in. At the top left of YouTube, click the 3-line icon, then click on Settings, then Notifications . . . under Your Preferences, be sure Subscriptions is turned on and under Email Notifications, be sure "Send me emails..." is turned on. If you install the YouTube app on your phone and sign in, you can forgo the email notifications in favor of app notifications if you wish.