I played "Road Ladies" from Chunga's Revenge for my friend, a great Jimmy Page admirer. After hearing the blues licks he instantly began taking Frank seriously, became a fan. That was 37 years ago and I'm listening to that song as I write.
I love all the experimental early music, social satire.
BWS, Chunga's Revenge, Hot Rats, Grand Wazoo*, Waka Jawaka, Over Night Sensation come to mind as favorites. Love all the older stuff, not so much after Overnight Sensation, One Size Fits All an exception.
Overnight Sensation was the point that established the next level in his incredible guitar technique. He had always been one of the most creative players in rock.
I would have to recommend Hot Rats as the next step. The earlier albums are essential if you want to understand his music. I love them, but cant help suggesting you jump to HR first, it's special.
* Not only is Grand Wazzoo a great album, I say him perform it live in 1972.