cards for games

I'm thinking you could find someone doing these kind of trades here: https://www.steamtrades.com/
I won't link anyone specifically as it may appear as if I'm actively helping getting "customers" or something. :P

The only site I know is pro-z. But it doesn't look very trustworthy to me. Use at your own risk.

Edit: https://oy-vey-keys.com/
You can trade in your trash game cards for coins and buy games with them.

I think technically tremorgames.com allows you to trade in cards for points and then use those points to get some of the finest trash xD