Do you think it is a bad thing to do, promoting gambling?
Provided that your country or religious didn't ban you from participating in gambling activity then you are good to go, i have seen famous rappers streaming and promoting gambling site and they are earning well from it. Except you see that you aren't comfortable with what you are doing or seen that your activity at office didn't give you enough time then you may decides on the next action to be towards your involvements on gambling promotions.
I agree with you, as long as a person's country and other things such as family or religion don't stop them from doing that then I don't see any problem with it. You can start streaming and promote casinos and earn money from it by partnering up with them, there are a lot of streamers who do this.
To prevent your audience from having a bad influence because of you promoting casinos you can warn them all the time that they shouldn't gamble much and whenever they do it, they should practice patience and responsibility because irresponsible gambling can be disastrous. A casino streamer should also have this as a text in the description or somewhere.