Trainers are grouped by amount of money they give. You want amount + your last digit of money sums to multiple of 5.

Pink Skier Pryce gym (just hold U or R):(28) 1
First sage in sprout tower:(3 3 3) 1

Blue skier pryce gym (R one tile then U):(26 26) 2
Psychic mahogany E:(24 26) 2
Spinner mahogany W:(14 16 16) 2
Bug catcher violet E (last resort):(2 2 3 2) 2

Youngster violet S:(6 8) 3
Bug catcher violet E then S:(3 3) 3

Youngster cherrygrove N:(4) 4
Psychic Ekruteak (not mahogany) (go south) S:(17) 4
SwimmerM cianwood N then E between islands:(23) 4

All pokemaniacs give multiple of 10