It depends on whether or not you want a big screen.
If you want the full screen experience, then get the pay the extra money and get iPad Air 2.
It has 2GBs of RAM, the newest processors, while the others still use the previous processors and 1GB of RAM.
The iPad Air 2 will last you a few years of constant software updates and OS updates, so you'll get your money's worth.
If you want a smaller screen the iPad Mini 3 will do and is cheaper, though there will probably be an iPad Mini 4 by year's end.
Anyways I bought the iPad Mini 1 back in early 2013 and I have gotten 2 OS upgrades, with iOS9 also running on it come this Fall.
It was also great for running eBook I used for my master classes.
iPads are great for running Keynote/PowerPoint, Numbers/Excel, Mobile Safari, Videos, eBooks (of all formats), PDFs, Video Chatting, iMessage, etc...
If you really want to save money you can buy a sub $90 Android tablet at most stores.
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