I recommend the paths where Pokemon already have higher levels (like down from Blackthorn City), Mt.Silver, Dark Cave (Blackthorn city side), and ofc Victory Road. Best is to train them in places where Pokemon type matters, like water or grass type is easiest to train in caves because rock Pokemon are weak for those types. Fire Pokemon beat grass types easily so grass paths are best for them. Electric-types are easy to train in water, and high-leveled tentacools and tentacruels can be found all over the place.
Best train for Pokemon is Pokemon league itself, as long you make sure you save all your money to your mom / spend it in potions etc. and just go and fight, pokemons grow levels while you win but if you happen to lose, there's no money for you to lose, and happiness points that lowers everytime your Pokemon faints, you can always gain back to your pokemons.
The best place I know is victory road
Mt. Silver or the Pokemon league
Seven Island if you don't include the elite four.
in the elite 4 It depends if you're playing gold/silver,/ fire red/ Saphire,/ Enerald,/ Ruby/ leaf green, or diamond/pearl
I'm not there yet but try the whatever they call victory road or the places you havent been to(that probably means they have strong Pokemon there). et
elite 4 or mt silver
elite 4
battle the elite four
The best place I know is victory road
elite 4
The Pokemon League
Mt. Silver or the Pokemon league
Seven Island if you don't include the elite four.
Really depends on 1 thing, if you have all 16 badges if you do go to the elite four they're Pokemon are 60+
The best place to train a shelgon is mt prye
The best place to train Pokemon level 40 and above is at Mt. Silver. Since you cannot gain experience through multiplayer battling, the highest leveled place is Mt. Silver. Pokemon average level 40-49 in Mt. Silver, so it is a good place to train.
The best place for more experience is to repeatedly challenge the Elite 4 + champion.