fire, steel, rock, fighting.
fire type
First see what Pokemon they have then remember the Pokemon and the type they are. Get the types that's good against the Pokemon they have and train them to level 100. Water beats Fire Water beats Rock Fire beats Grass Fire beats Ice Fire beats some Bug Grass beats Water Grass beats Rock Ground beats Fire Ground beats some Bug Psychic beats ghost ... ... ...
flying
Grass, Flying and Rock types.
Electric
The best place to train a lv 30 fire type in Pokemon diamond would be next to snow point city because there are lv 30 Pokemon there that ice and grass but run away from the sneasel.
rock
ground
Fighting and Fairy
Bug, Ground, Psychic, and steel
Fire type Pokemon or fire type moves beat electric Pokemon.
Grass