After passing through Dernière Way after you defeat Wulfric and get the eighth badge, you reach Victory Road.
To access everything in Victory Road, bring pokémon that know Rock Smash, Strength, Surf, and Waterfall.
Battle for Entry
When you enter Victory Road, go west to find Ace Trainer Robbie. You have to defeat him to be allowed into Victory Road. He has a level 56 Carbink, a level 56 Raichu, and a level 57 Kingdra.
After defeating Ace Trainer Robbie, go north to pass through the badge check gate. When it opens, go north to go outside.
Go north up the stairs to enter the cave.
Go north and you will encounter Ace Trainer Alanza, who has a level 60 Weavile.
Go west and Surf west in the water. On the other side, use the Dowsing Machine to find a hidden X Attack on a rock.
Go north up the stairs. You can avoid Ace Trainer Bence by going up the stairs on the right and using Rock Smash. Bence has a level 56 Steelix, a level 56 Electrode, and a level 57 Kangaskhan.
Go up the stairs that are north of Ace Trainer Bence. To the south, Black Belt Markus is running around. He has a level 60 Machamp.
To get an item, go south from Markus. Then when you reach the water, go west or south. Battle Girl Veronique is running around this area. She has a level 57 Hawlucha and a level 58 Mienshao.
In the southwest corner of the watery area, you find a Dusk Ball.
Go north, back to where Black Belt Markus is running around. Go west from there and you'll exit the cave.
First Outside Area
On the bridge, Backpacker Farid is running up and down. He has a level 58 Haxorus.
North of the bridge, use the Dowsing Machine to find a hidden Hyper Potion on a small rock.
Continue going north. Use the Dowsing Machine near the next cave entrance to find a hidden Full Heal on a bush.
Go into the cave entrance.
Just inside the cave, Battle Girl Sigrid is running from side to side. She has a level 60 Medicham.
There are some stepping stones north of the Battle Girl. Go up the middle path, then go left when the path splits. Continue north to reach the ledge.
From there, go north, then east. To the north, Black Belt Ander is running up and down. He has a level 57 Pangoro and a level 58 Heracross.
Go north past the Black Belt to find a Carbos. Use your Dowsing Machine up here to find Smooth Rock on the north wall.
Go back to the south. There is a rock that you can get rid of with Rock Smash. Break that rock, then go south on the ramp.
Turn on the Dowsing Machine, then go west and north up the narrow passage to find a hidden Ultra Ball on the stalagmite.
Go west through a gap in the leftmost stepping stones, then go south and proceed east past the stones. Go up the stairs to the east, then hop across the stepping stones next to the eastern wall. Go south to go back outside.
Go along the narrow path south. You'll reach a cave entrance where you find TM03 Psyshock.
Go back the way you came to return to the previous cave. Hop north over the stones, then go west and hop over the ramp. Continue west and hop on the stepping stones to reach the northwest ledge. Go north, then east toward the boulder, then south, then use the stairs to the east. Go north and hop across the boulder, then go east. You'll find Psychic William. He has a level 58 Espeon.
Use the stairs south of the psychic. Go west and use Strength to push the boulder west into the hole.
Walk west over the boulder, then go up the stairs. Up here, you find Brains & Brawn Arman & Hugo. They challenge you to a double battle. They have a level 58 Medicham and a level 60 Gallade.
After the Brains & Brawn duo, go north past the bridge and go west along the narrow path. Go outside to find a Rare Candy.
Go back inside and go back to the bridge. Cross the bridge, then go north up the stairs, then east through the exit.
Second Outside Area
Go east. You will see Fairy Tale Girl Corinne running around. She has a level 56 Azumarill and a level 56 Florges.
East of the Fairy Tale Girl, there is a boulder to the south. Use Strength to push it south into the hole. Walk south across the boulder. Use your Dowsing Machine to find a hidden Revive on a rock.
Go west and into the cave. The path in this area is straightforward, so just keep going until you reach a boulder that you can push with Strength. Push it south into the hole. This gives you a helpful shortcut to the second outside area.
Go north again, following the path to return to the second outside area. Go north past the Fairy Tale Girl. To the west, there is a cracked wall that can be broken with Rock Smash. Break that wall, then go west to find a PP Up.
Go east through the wall. To the north, you can battle Hex Maniac Raziah, who has a level 58 Gourgeist.
To the east, you find a Pokémon Ranger who doesn't battle you, but instead heals your pokémon if they need it.
Go east and north to get the Quick Ball behind the stone platform.
From there, go south. Your neighbor will arrive and challenge you to a battle.
Battle your Neighbor
Your neighbor has a level 59 Absol, a level 58 Altaria, a level 57 Meowstic, a level 61 starter that is strong against your starter, and a level 57 evolution of Eevee (Jolteon if you chose Chespin, Flareon if you chose Fennekin, or Vaporeon if you chose Froakie).
After the battle, your neighbor gives you some Max Revives.
Go west and talk to the Pokémon Ranger to heal up your pokémon after the battle.
Continue toward the Pokémon League
From the place where you battled your neighbor, go south, then west. Use Rock Smash on the cracked wall to the north, then get the Zinc beyond the wall that you broke.
From there, go east into the next cave.
In the cave, go east up the stairs. You will find Pokémon Ranger Petra running up and down. She has a level 57 Slowbro and a level 57 Altaria.
Go east past her and jump down the ramp that is east of her. There are two ramps to the south. First, take the south one. Keep going south. You'll reach some stairs. Go up the stairs and follow the path to reach an outside area.
Out here, use your Dowsing Machine to find a Pretty Wing on the rock to the left.
Go north from there to find a Max Elixir.
For a shortcut, slide down the ramp. Talk to the Pokémon Ranger out here to heal up. Then go south and into the cave. Go east to return to Pokémon Ranger Petra. Go down the ramp that is east of her, then go over the east ramp. Then go south over a couple of ramps. Use your Dowsing Machine there to find a hidden Escape Rope.
Go east over the ramp, then go east up the stairs. If you don't care about collecting all of the items in the cave, you can go east to battle the trainer and then use the cave exit east of that trainer. Otherwise, go north instead of going up the second set of stairs.
To the north, use your Dowsing Machine to find a hidden Max Repel on a stalagmite.
Go north from there to battle Veteran Inga, who has a level 61 Talonflame.
Now go west form Inga and slide south down the small ramp. Keep going south to find a Dragon Fang.
Go south over the next ramp, then go east up the stairs. From there, go south. You will find Pokémon Ranger Ralf running around. He has a level 59 Crobat.
South of the Pokémon Ranger, you will find a Full Restore.
Go north to the stairs, and go east up the stairs. You'll find Veteran Gerard. He has a level 57 Banette and a level 59 Leafeon.
Go south from the Veteran and use Strength to push the boulder south. Walk south over the boulder and follow the path to reach an outside area. Go west and use Strength to push the boulder west into the hole. This creates a shortcut. You can go north to find the Pokémon Ranger who will heal your pokémon.
Go back into the cave that you came from, using the shortcut that you just created so you can use the southern cave entrance. Go east, then north to reach the eastern exit of the cave.
Third Outside Area
Go south to find Artist Vincent. He has a level 58 Smeargle.
Use your Dowsing Machine to find a hidden X Defense on a rock south of Vincent.
Go south across the bridge. You will encounter Ace Trainer Michele. She has a level 58 Macargo and a level 58 Scizor.
Go west from the Ace Trainer. Surf in the water and use the Waterfall move to go up the waterfall east of the cave entrance. Surf north, then go east onto land. Here you find Hiker Corwin, who has a level 56 Torkoal and a level 56 Golem.
Use your Dowsing Machine to find a hidden Max Ether east of Hiker Corwin.
Go north to get TM02 Dragon Claw.
Now get back in the water and go south down the waterfall, then go into the cave entrance that is to the left of the waterfall.
You're almost there. Surf north to go onto land. Keep going north to find Veteran Timeo. He has a level 57 Trevenant and a level 59 Gigalith.
Go north again. You'll find Veteran Catrina, who has a level 57 Glaceon and a level 59 Snorlax.
Continue going north to find Veteran Gilles. He has a level 55 Skarmory, a level 55 Umbreon, and a level 57 Alakazam.
Turn on your Dowsing Machine and go north to find a hidden Star Piece in the middle of the four torches.
Go north and you will reach the entrance to the Pokémon League, where you will battle the Elite Four and the Champion of Kalos.