The ease of use of a tablet depends on the operating system software that it runs (rather like Windows runs on a PC or laptop).
And the three main tablet operating systems are:
a) iOS that runs on all Apple tablets (and Apple mobile phones).
b) Android that runs on many tablets such as Samsung, the Tesco Hudl, the Amazon Kindle and many others (as well as on mobile phones)
c) Windows 8 that runs on Microsoft and other tablets.
But all tablets are designed to be easy to use. Most people could pick up a tablets and start using it within minutes.
Apple tablets are famous for their ease of use, but they do tend to be the most expensive.
Android tablets are also easy to use, and generally cheaper than Apple tablets.
Windows tablets are new to the market and still trying to build themselves up a user base.
So the main consideration is not particularly ease of use (as they are all easy to use) but how much you are willing to spend.
The cost does vary depending on how much memory, quality of screen, speed of CPU and so on.
You can spend about £100 up to £300 or £400 for an Apple tablet with lots of memory.
So how much do you want to spend?