YouTube.
I propose you to try and find communities on Facebook matching the subjects of your YouTube channel, such as Scuba Diving, Travel and so on.
Once we have found them, we will show them on Facebook, Instagram and Messenger, an ad presenting your channel through the subject they like.
About the pricing, two possibilities :
1- I do the ad, and I manage the Facebook budget. And I take a 20% mark up on the cost per lead on Facebook.
Example: if the ad brings you 100 subscribers at 1$ each, I will pay 100$ to Facebook, and you will pay me 120$ + 65$ setup= 185$
2- I do the ad, you take care of the budget. I will cost you 50$+15$ per day of running the campaign.
Same Example as above, for a 3 day campaign : you pay 50$ setup and 45$ monitoring to me, and 100$ to FB.
The price comprises :
-market research to find your target group on Facebook (including finding similar channels on YouTube and find their followers)
- ongoing monitoring to optimize the campaign in real-time
- delivery of a report about the profile of recruited people, to be sure that they are on target, and not artificial subscriptions.