You basically need the ability to mix two sources together. Any controller, from the Mixtrack Pro up, can do that. Look carefully at the extra features and costs as the price rises and ask if you need them. DJing existed before newfangled controllers and mappings, and will exist when the flavour of the day has changed. The crowd, the music and the programming are what counts first. Try not to be blinded by marketing and tech, when what’s really important is getting in front of a crowd and “doing it”.
That’s not to say esoteric mappings and expensive controllers aren’t great, but they’re not necessary. You may decide you want to learn to DJ with a USB stick and club gear, and only have a controller because it’s convenient for home practice, for instance. In this case you may bemoan that you bought a top-of-the-range controller. But until you’ve DJed for a bit, this kind of question is impossible to answer.