I've had great success with AdWords!
Last December when CPM's were insane and adblock usage was low I could actually bid for views for less than what I got paid in ad revenue (on a day by day basis) .. I received hundreds of dollars in "free" views from Adwords on FreebieFM.
The biggest "secret" with adwords isn't really that much of a "secret" but you can put in a max bid of $0.01 per click. (whereas naturally the normal minimum auto-bid by google is either $0.02 or $0.03 depending on currency)
If you can secure $0.01 search result bids then you need to look at your average ad views per user and your CPM.
If avg. user has 10 ad impressions (before they leave your channel forever) at a $5.00 cpm (which you won't get anymore) than..
You'd be paying $0.01 for the view
You'd be making $0.05 in ad revenue from that view (over a day, week, month.. you decide the variable and what works)
= $0.04 and 1 viewer "profit"
I personally was making $0.02 profit per viewer I paid for with adwords.. Problem was, I couldn't full materialize it as I only bid $0.01 so the "auto-bids" of $0.02-0.03 automatically bid me out in most cases.. Therefor I was only receiving ~300k impressions which resulted in about ~4000 clicks per day instead of many times that with a $0.02 bid.
Of course you optimize your adwords to only show to "high value countries" or this technique doesn't work.. English only is a must as well to secure views worth more than what you paid.
This is how to use adwords to make money or break even, it's a fabulous way to advertise in almost any circumstance even if you do mass-quantity high-bid campaigns and lose a little money.
Also, I was spending $CAD and I was paid in $USD.. This accounted for a 5% value gain due to our currency value and the fact that google allows $0.01 CAD bids.
I've never wrote or spoke about this to anyone lol but i've disabled ads on my channel until cpm's return to a reasonable amount.. I'm not going to blast people with advertisements for pennies on the dollar, it doesn't make sense. If you are making a $1.00 eff CPM like most of us then you might have a hard time breaking even.