Good cheap pc / laptop?

There are PCs or laptops for a maximum of 200 euro or so (plus minus).

should be suitable for games or live streaming

used is also possible

and please link where to buy

Unfortunately I have to tell you that you don't get very far. With 300 you can build yourself one that is fairly gamble.

Do you have a link where you can get all the parts cheaply?

Ebay.de

Check out Hardwaredealz.com which shows you the best parts at the best price. But don't order the parts on Amazon or Alternate as he shows it, but on Mindfactory.com