Note that you can add your gmail email without having to install the full Google Services. Here's how you do it:

• Install a good email client, like fairemail or k9mail.
• Generate an app password in gmail (you need to have 2-factor auth enabled). Here are more details on how to do this
• Setup a new account in your email client using IMAP and the app password.

Done, now you can use gmail email in GOS without installing Google Services.