Its easy to think of becoming successful in affiliate marketing with youtube channel that has lots of subscribers, it could be possible. In reality, its not easy. I personally have been there which is why podcast are much better and many have been successful with just choosing a trending topic and discuss it with a guest. However sticking to a particular niche like casino can't be get that much audience.
This is possible, but when we see the one successful youtube channel, we don`t see thousand of the same channels which have no subscribers ever and no one talks about it.
And the same time you need to work hard every day to create new content. If you stop - your channel lose subscribers every day. And the profit falls down every day too.
It could be done however, there's a lot risk that comes with it. Since nowadays most people really aspire to be famous and generate a decent amount of income, most people pursue being a vlogger and content creator. In fact, there's a lot of newbies trying to gain more subscribers each day because they seem to think it's an easy way out of hardship in life because of the amount of money it pays.
However, creating a content isn't really easy as what it's suppose to seem. You have to be creative as much as possible and think of a subject matter that would get the interest and attention of the audience. If someone is going to stick in gambling as a subject matter, the audience would be limited since not everyone gambles. Searching topic about what to create could be a challenge too since gambling is controversial. It is possible, but it has its cons.