Correction: “Moving up Across from 9x9” 
As someone who’s not suited to rote memorising masses of joseki, I found this book particularly helpful: “Fundamental Principles of Go” by Yilun Yang.
Also, bear in mind that the ranking pools are different for different board sizes (and speeds). ie. it might only be that with more beginners playing 9x9, your rank was artificially inflated compared to 19x19. See also: Rating breakdown conversion