EZBlocker will either block or mute ads on Spotify.
EZBlocker is portable and very simple to use. Aside from the option of opening your volume mixer, you can mute only, disable all ads and start EZBlocker on login.
That's about it, but then again, we appreciate the simplicity of just doing a single function. However, EZBlocker can also block audio in ads as well as songs that you don't like. The one downside is you have to sit through the current song first.
EZBlocker won't catch every ad yet, but it's probably the best bet to block Spotify ads.