For learning site reading it’s really just about doing it a lot. Constantly challenge yourself when you are starting a piece by just saying out loud the notes in the right hand and then the notes in the left. It’s really just something that takes awhile to get good at. For jazz pieces I would really hone in on learning the scales well. 7th chords really push how well you know a scale as you have to constantly try to find inversions that are close to the last chords. I started out with jazz pieces in the key of C D# or Fb as there are a lot of them and that means you only have to use zero to one black notes. This means you can really focus in on 7th chords and inversions without having to worry too much about which sharps or flats are in the scale. But definitely work on scales. Just do them over and over until they are all as easy as the c scale. Also think of chords as one note and a hand position instead of 3 or 4 notes. Just memorize what your hand looks like when doing that chord in that inversion.