The further I got into the series, the more I started to notice how much Dune has fed into other stories, films, and shows. You can see the building blocks of so much modern sci-fi in it. For me, the strongest run is still Dune and Messiah, following Paul Atreides. After that it drifts a little before pulling things back together again in Chapterhouse.
I would absolutely recommend at least the first books. They stand on their own, and now they also make a great companion to the recent Denis Villeneuve films, which have done a strong job of bringing that world to a wider audience.