I'm a consultant for Youtube sponsored channels. Engagement is the key. To get engagement you'll need:
1) Consistency of posting is one of the most important factors, you'll have to keep posting consistently for people to form a bond with your personality (or the personality of your channels characters, etc).
2) In order to be able to consistently post quality videos, you'll need to love what you're doing. You'll need to love making the videos you're making, just for the sake of making them, without even thinking about how many views you're getting. See this video for a good discussion of this: https://www.youtube.com/watch?v=WijPMprRgGo
2) As you feel a bond with your viewers start to form (more views and comments) you'll want to start actively engaging with your viewers, asking for their opinions to be posted in the comments, etc.

If you want to discuss any of this more feel free to give me a call.