Spend enough time to create 5-10 pieces of awesome content, and spend the rest of your time networking. Leave thoughtful comments on authoritative blogs that you enjoy reading. Reach out and email influential bloggers without asking anything in return. After a month of being selfless, try to secure a guest post on those authoritative blogs and capture some of their audience (your guest post should be amazing).
The time you invest to make any significant amount of money is the same amount of time it takes to build a course or other offerings. If you want to make good money with ads (in the thousands), then you need to get 100s of thousands or millions of pageviews a month. This takes time and in that time you could just as easily build up your mailing list, create an infoproduct and make thousands whenever you want.
Working with advertising networks isn’t your only option when it comes to selling ads. If you end up with enough traffic, advertisers may come directly to you and ask you to place their ad on your site. You can also contact advertisers yourself. The biggest difference from the above mentioned option is that there is no middle man, which means you can set your own ad rates.