I went to the Giant Chasm. You will need HM Surf.
Here's a guide:
Outside the Cave:
Light Grass: Lvls 50-55
Dark Grass: Lvls 55-60
Inside the Cave:
Inside the Chasm:
Light Grass: Lvls 55-60
Dark Grass: Lvls 60-65
Use a Lucky Egg and/or a Exp Share. That should train a lot. Once your
Pokemon are around level 70, challenge the Elite 4 and keep on using
one Pokemon only. Audino's are another exception as they can give tons
of EXP though being at low levels.
- GAMEFREAK Morimoto
- Elite Four
- Level Up at Join Avenue Shops.
- Rare Candies (Not Recommended)
- Lucky Egg/ EXP Share
- Basic Wild Pokemon
- Black Tower or White Treehollow.
These are all the best ways I could think of. There are many more such as the Battle Subway and Daycare trick but make sure you EV train before attempting it.