Your question is unclear. Sounds like you're thinking in terms of the old POP3 email setups where emails would be deleted from the host after being downloaded to the computer?
Default gmail setup on iOS devices uses IMAP, which is different from POP3. Effectively the ipad presents a view into your mailbox on gmail with copies of the most recent emails cached on the ipad. Any actions you take on the ipad are also effected on the server; read an email and it's marked as read, archive an email and it's archived on gmail, etc.
Is that what you're looking to accomplish? Or do you want no changes to be made to the email on gmail?
If the former, then just set it up as a new account under Settings->Mail,Contacts,Calendars->AddAccount and select Google