Do NOT go “Buy” a Kodi Media Player. The peddlers that sell those are often crooks that install illegal software. Kodi Developers go nuts over these folks because they quite often promote piracy.
What you do is buy your own hardware, and then you install Kodi on it.
You can run Kodi natively in Linux, Android, and Windows.
Or you can download pre-packaged distributions like OpenELEC, LibreELEC, etc and run it on any number of hardware platforms.
Depending on your needs, it can be anything as small as a Raspberry Pi ($50 for a whole kit), a Amazon Fire Stick, or any upwards of $1000 for a full HTPC setup. It’s all up to you.
All I can tell you is that Kodi is as simple as you might want, but it can also support very complex setups if you need.
Go over to www.kodi.tv and have a look around.