Are u serious or just too lazy to do ur math?
The iPad Air 2 is not heavy. It weighs 0.96 Pounds (437 Grams).
When you make purchases for any additional cases for phone/iPad, the manufacture typically list the weight and dimensions of the case. That's what I would look for, because there are thousands of cases on the market available for the iPad.
I have the leather-y Apple Smart Case (I think that's what it's called?) case on my iPad Air 2 with the magnetic flip lid thing. I love it. Almost 3 ½ years later, it's still great and the only one I've ever used on it. I like that it is also slim enough (albei sufficiently durable) to slide into a zippered iPad case if need be whilst traveling. HTH!
You know how clumsy you are (or aren't) and how often you are in situations where your iPad might be damaged. THAT will dictate what type of case, if any, you should use. It might very well be proper for you to use an Otterbox if there is a high probability of damage to your iPad.
$33 from eBay, new, smart case in leather for air 2: