Should I buy a screen guard for the ipad 2018

Yes the smart cover is enough protection.

 

Wouldn’t hurt.

 

The smart cover is more than enough to protect the screen on the 2018 iPad.

However... if you plan on using the Pencil with the 2018 iPad, then I recommend getting a matte screen protector. Not only does it cut down on fingerprint smudges, but it offers a little resistance for the Pencil so that it feels a little more natural. "PaperLike" is a popular one but it is quite expensive. I'm having a great experience with Mr Shield iPad Air/Air 2 Anti-glare... (Air/Air 2 protectors fit the 2018 iPad) 5 protectors for $7.