Welcome to Android Central! Sorry, I'm a bit confused. You want a Google account on your tablet that's different from your main Google account? All Google accounts are associated with an email address. You can create a Google account and associate it with any of your email accounts (like Yahoo, Hotmail, etc.). Just because there's an email address, you don't have to use it. You could disable the Email and Gmail apps on the tablet, or turn off the email sync.
To create a new Google account, go here:
https://accounts.google.com/signup?service=mail. Once it's created, add that account to your tablet in
Settings>Accounts, and remove your primary Google account (if it's on there). Keep in mind that if you have already purchased apps from Google Play using your primary Google account, you may have to purchase them again using the tablet's Google account, since they won't be the same. Purchases stay with the Google account, not the device.