I plan on creating a channel revolving around a "top list" ( in english ) not really on a specific niche just things that I think people would be interested in ( I haven't completely decided on this yet ).
Now back to the question in the title:
I want to know roughly how big of a channel would I need to make that amount? Is it even realistic to think that I could succeed ?
As others have said, it all depends.
If your videos happen to be in the right market and are watched in the U.S., Western Europe, or Australia, you could make $300 in as little as 100k views. If it's a more typical market you're reaching, you might need as many as 600-750k views a month. If most of your views come from Mexico, Central America, Africa or the Middle East, you might need up to a few million views.
There are far too many variables to be able to say anything with confidence.
It should also be noted that videos also tend to earn more the higher their view counts go. If a brand new video and one that had 1M views each gain 50k views in a month, the new one will earn significantly less.
Lastly, there are already countless "top lists" video channels and it would likely be difficult gaining traction in an already competitive market. Not to mention that, depending on the topic of the list, you could easily run into numerous copyright issues and hurdles.
I'm not trying to dissuade you. I'm just giving you an honest idea of what to expect.
Best of luck.