Some stray thoughts from someone who enjoyed scales and disliked Hanon in my younger days.
Most people start with Cmaj. From my pov an unpleasant choice. Which scale makes your hands/nervous system most happy will of course vary. For me it was:
Most liked: Bmaj, C#maj, F#maj, Emaj in decreasing order. Also Dmin
Most disliked: Cmaj, Eb, Bb
Decide what scale you most like (pick one). Stay with that (if can't decide just take Bmaj) and move on to...
1 hand, 2 hands in 1,2,3,4 octaves
(2 octaves in pairs, 3 in triplets 4 in quadruplets etc). Helps to strongly emphasize 1st note of grouping.
- Staccato legato, different in different hands
- Different dynamics (loud soft)
- Non-octave distance between hands (3rd, 6ths common but you can do any)
- Different groupings eg 1 in right hand 4 in left
- Polyrhythm : eg triplets in rh quadruplets in lh
More than getting good learn to feel happy practicing!