ADWords works but don't expect any subs or much interaction on your videos at all. Depends what kind of content you have but honestly you won't get much interaction on your content. I tried it on 1 video and it didn't do much apart from give views.
Exactly. I had two Sonic game reviews that even managed to get a very good amount of watch time, but there was little engagement and maybe 5 subs between the two campaigns. With more money spent than I realized.