I no longer use an exchange unless it's for trading purposes, but buying and selling is done through a local exchanging service where you receive the money you cash out within 24 hours on working days.
Spot exchanges are getting so cocky with all their stupid questions that I am even considering ditching them entirely, but I got a little bit of interest in trading lately so I'll wait it out for a longer while.
If you are referring "simple" for the user interface then I find Yobit the most simple to use platform, you don't have anything to do there except to wait for a pump. When you see a pump get in. However, Yobit is not trusted.
Yobit might be simple to use, whatever that means, but it's one of the worst exchanges in the crypto world. If we look past their shady nature, it's also quite slow and very unreliable.