What you need depends on what you're streaming, how invested you are in streaming long term and of course money. If money is no object you can go crazy with the stuff from Sephiroth's list. If you're just going to test the waters, PC gaming simply requires OBS, learning how to use OBS and a solid internet connection. Headsets with a microphone included make your life a lot easier as the next most vital thing. For PS4 (and XBO, I imagine?) there are in-built options for streaming which are fairly easy to learn.

I would suggest learning with those systems before you go investing time in a fancy stream getup including capture cards etc. Although if you intend to stream from earlier consoles, you'll probably need it. If you're not really bothered so much about a specific game, try to focus on learning streaming with PC and current generation consoles first so you can learn those systems, then grow from there.