normally I would recommend the 1st gen ipad mini, cos once you add an anti-scratch/ glare coating the screen will look different anyway.
however, apple only offer the 1st gen in 16gb which isn’t much once you factor in the operating system.
so the smart money would be on at least 32gb, and the new version has more power which cant be bad.
I’ve got a 1st gen in 32gb and I cant fault it except that it makes the ‘rebirth’ app a bit akward for my clumsy hands.
I’m sure you can open an apple account without buying any of their products. This can give you the opportunity to select apps to add to your ‘wishlist’, which may in turn may give you an idea as to how much memory your future purchase requires.
best of luck 🙂