Not to long ago Valve (Steam) tried to sell the streaming box called Steam Link, it was designed to stream your PC games right to your TV. Well, the Steam Link box never took off and a few months ago stores like Gamestop were selling them as low as $15 dollars, just to get them out of the store.
If you missed the opportunity to pick up a Steam Link there is still hope as Valve has just release a Steam Link app for the Raspberry Pi! Now you are going to need a Raspberry Pi3 or the Pi3+ running the Raspbian OS to install it, this does not work with the pi zero, Pi1, or Pi2.
Of course, this is still a work in progress and you may see a little extra lag compared to the Steam link box but most are reporting good results with this first release of Steam link for the Raspberry Pi.
You can find instructions on how to set up your Raspberry Pi with Steam Link here.