What HW do I need to buy to start playing with nRF52 DK?

I'am realy new to nRF52 development. I want to start with a simple demo as shown on www.nordicsemi.com/.../Getting-started-with-the-nRF52-Development-Kit.

What HW do I exactly need to buy to start playing? I have no experience with JLINK at all. Maybe if someone could explain me a little what is JLINK good for?

Thank you in advance.