Should I return my hard worked for iPad?

So I got an ipad from staples at the end of August and unfortunately sometimes it lags on ios 8.4 and today I was playing a game and it crashed. It is also only 16gb. Sometimes the interface lags a bit and the animations are not that smooth. It is kind of different than what I saw on the reviews. I do not want to downgrade to an older ios 8 version because it restores all my data and loses all saved progress. I also do not want to update to ios 9 because it is 1.1 GB to update and thats too much I currently have only 5.5 GB of space left. I am wondering if I should return my ipad and get an ipod or a samsung tablet. Thanks.
Added (1). It is an iPad mini 2 with ios 8.4 from Staples

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