is there a good ad blocker for safari

I would look for one on the App Store.

Caveat: I don't use them. 1Blocker seems to get the most positive reviews though.

The was some emerging evidence a few years back that having more than one ad blocker can cause performance issues. If you use one, one is enough.

I've not used them either. Many pop-up notificaitons can be stopped without adding software. See John Galt's excellent user tip on the subject:

Stop unwanted Notifications - Apple Community

I avoid ad blockers because I don’t trust them to not share my privacy while browsing.

My alternative ▷ Distraction Control.

Good luck! 👋🏼😉