ok so my laptop is dieing (apple air13in) so saveing up for an ipad, due to me haveing vison problems i need the 12.9 (bigest sizw) so i can see you tube and what i am doing but i know nothing about Gb my uncle does so i have asked him as well but also gonna ask here, i use my compter right now for email , hp , fb and i use too for you tube but you tube was makeing it crash more so i you tube on my tablet right now. anyways heres the Gb sizes for the size of ipad i need https://imgur.com/LFOHLSL 64 gb is as much space my phone has but i dont do anything ohter then basic net and email then my hearing aid app i be useign the ipad for Hp . youtube . Fb , email . and i would love to put my farm game (farmvillie) and some movies on it and some of the ohter games i play on my tablet 4-5 games but i play the farm one the most. Would the 254 gb be just fine for this? or shall i go for the 512 gb (

Basically you're just talking storage here, so it depends on how much data you want to hold.
In your case - web browsing, such as Facebook, checking your mail, HP and even Youtube, stream their content to you. It is grabbed off the internet on demand, and (mostly) doesn't depend on being stored on your device, thus these things don't use much storage space.
Games you download and install do require some space, but being mobile-oriented, they aren't nearly as big as computer games can be, so again, they're not all that bad on storage.
The only thing I see in your list are movies. Those are by far the most storage-dependant thing you want, so I'd say this is your answer. How many movies do you want to be able to carry around? Unless you're wanting to bring a whole collection at all times, even these aren't nearly as bad as you might think.
You can always check how much space you're actually using on your phone, but from the sound of your post, I'd guess even the 64GB version would get you good mileage, especially considering the increase in price for the bigger ones.

Simply put, I'd personally assume each game or movie you want on the device takes up 2GB, and get a very, very conservative estimate of how much you can fit on there, as most apps and movies are smaller than that.
On the other hand, if the pricetag is of no concern, then bigger is never worse.

uncle said the most is better. so i prb go with the most and oh well if i dont use all the space i would have it there lol  so i prob go with the 256 gb or 512 gb depends on how long i can make my comepter last. it still be an while so still gonna do homework so feed back is more then more welcome. and for movies prob no more then ten i only want a few on so i have something to do if my power dieds or i traveling or the young adult i nanny (she speacl needs) has a few movies on there for her and an game or two :) the pitures will be put in cloud or fb so not worryed thhere, the priceing just will mean when i get it lol as i am about 1/2 there to the one with most space. then so i looking at avout anther 700 till i get one with the most space and that will include an wartttey