If you stream live on Twitch, you can earn around $70-$80 for every 500 viewers watching you.
This is based on an estimate that a friend has just given me from one of his channels, but it does depend on a couple of things.
How much money can Twitch streamers make?
When you're using a service like Twitch to make money on your gaming streams, then you need to have a certain amount of regular viewers in order for it to be worth it.
Also, if a lot of them use AdBlock, then you won't be making very much money at all, because they won't even see the ads!
If you're interested in setting up a live stream and making some money through Twitch or another app, then I'd suggest getting involved in the general community first, trying to build up a following, and hopefully that will convert into lots of viewers once you are ready to serve ads on your broadcast.