I'm currently in the process of starting a side business doing this with some friends so have done a lot of research in this market. I'd be very interested in hearing others experience as well. Though my summary researching is:
tl;dr really is, if you're not going for what is essentially a clickbait strategy, the seeming best strategy is to simply produce the highest quality of content you can and do it *consistently*, whether consistent is once a month, one a week, whatever. Common failure point I keep reading about is channels achieving some success and then over-extending themselves(trying to do daily videos without the audience or market to support it as an example which just gives them brand fatigue). Additionally budget for marketing of some kind(budget as in budget money or time), be it just being an active member of the communities you're catering to, or whatever, do *something*.
That really seems to be the only "magic secret" to it, do it the best you can, consistently, and put out the word. It takes well over a year of effort to grow from nothing to even turning a gross profit, depending on equipment costs and subject matter and if you're paying artists or editors.
That's if you want to do it the "proper" way. Personally I'll be spamming videos "10 Things you didn't know you wanted to know about Final Fantasy Adventure [GONE SEXUAL]".