Poliwag > lvl 25 > Poliwhirl > (water stone > Poliwrath) (trading with King's Rock > Politoad)
Sorry to burst your bubble, but it doesn't evolve, because it's the last evolve form of poliwag.
Level 30.
Level 30.
level 28
Level 25
Level 37.
Level 18.
Level 26
at level 40 it should evolve into drapion
Spiritomb doesn't evolve.
Donphan doesn't evolve.
you have to evolve it with a water stone