Once upon a time I tried to use Google ads to promote the parent site for my YouTube channel: https://www.youtube.com/user/devfactor

I spent $100 on ads, which resulted in around 25 new subscribers. The next week, I wrote a really in depth Arduino Morse code tutorial which ended up on some social networks and netted me ~100 subs.

I'd say that Google adds for me where NOT worth the price. Generating more organic content worked better.