I have just installed my Pi-Hole server on a Pi-Zero and have it working on my local network. I have set my router's DNS to the ip address of my Pi-Hole device.
I looks like I am getting less adds served to me on general web pages. But I am still getting youtube videos which start with adverts.
I do have multiple routers on my home network which I use as wifi extenders. Only one router acts as the DHCP server -
Youtube is cause of constant discussion here on the forum, for two reasons:
As Pi-hole is a filtering DNS forwarder, it cannot block any ads that are delivered via the exact same domain as the content, unless you are willing to forfeit accessing the content as well.
Any counter measure published here is likely to be picked up and conteracted by Youtube sooner or later.
Feel free to search our forum here for Youtube, you may yet find ways of defeating parts of it.
YouTube serves the ads from the same domains as the content, which makes it difficult for a domain blocker (i.e. Pi-hole) to block the ads without blocking the content. There is a long running thread on this topic here.
There is also a user-submitted method for blocking YouTube ads - many users have reported positive results