how do i reset a used ipad given to me as a christmas gift. i am unable to finish activation becau se the previous owner's gmail account still shows

Settings, general, erase all content and settings.

if the person has iOS7 on that device and it's activation locked then you'll need the apple ID of the previous owner to fully wipe it. So if you can't wipe it you'll need that previous owner to give you their apple ID or to unlock it for you.

If you can't contact them or if they can't unlock it, try to get your money back because without that info you can't fully erase that ipad, and it's unfortunately possible that the device they sold you wasn't theirs to sell.

The previous owner needs to do this.

What to do before selling or giving away your iPhone, iPad, or iPod touch

http://support.apple.com/kb/HT5661

 Cheers, Tom 😉

Let the Ex-Owner Erase and Set it as a new iPad for you