Water Pokemon. You can also use rock Pokemon such as geodude or onix.
Do not use grass or steel Pokemon these types are week against fire.
Fire types, they burn bugs. Burn baby burn!
The most effective in rock type Pokemon is water Pokemon ofcourse.
electric and ice are effective against flying
first you pass the first five gyms then you either get your best fire type Pokemon or fighting or ground they are the most effective against steel type Pokemon then you pass it.
I would say poison type, as normal type moves are not very effective, neither are fire attacks, and bug types are weak against rock. Therefore, I conclude that poison type, depending on your pokémon's attacks, you should go with your poison type pokémon.
Fire and fighting type moves are super effective against Ice type pokemon.
Fire types, they burn bugs. Burn baby burn!
The most effective in rock type Pokemon is water Pokemon ofcourse.
electric and ice are effective against flying
Water
fighting types and bug types are the most effective types on dark.
electric type of course!
Fighting and Ground type moves are most effective against dialga, since it is a dragon+steel type pokemon.
dragon and ice is most efective against dragon.
first you pass the first five gyms then you either get your best fire type Pokemon or fighting or ground they are the most effective against steel type Pokemon then you pass it.
There are two.Sableye and Spiritomb. Ghost- and Dark- type. The only exception is a Pokemon that has recently used a move such as Foresight, then uses a Fighting-type move, which are ineffective against Ghost-types but super-effective against Dark-types.
I would say poison type, as normal type moves are not very effective, neither are fire attacks, and bug types are weak against rock. Therefore, I conclude that poison type, depending on your pokémon's attacks, you should go with your poison type pokémon.