Is there a ratio of advertising income you can expect on YouTube based on views/subscribers? For example, for every 1000 subscribers how much ad revenue can you expect? Is there a ratio that works? What other ways can you earn revenue off your audience?
The amount of money that you make on YouTube definitely varies, but typically most people say they're getting somewhere around $2 per thousand views on average. It depends on a number of factors such as where those views are coming from (ie. which countries), who they're coming from (ie. age and sex), what your content is about, and what else you've got going on with your channel in terms of the videos, views, subscribers, etc.
Many YouTubers earn revenue from selling merchandise, music on iTunes when relevant, affiliate promotions, and brand deals (ie. sponsorship and product placement). The majority of the bigger content creators on YouTube don't make most of their income from Adsense because they can often get a sponsor to pay MUCH higher CPM's ($ per 1000 views) or even a good flat rate amount for promotion/endorsement in a video.