After passing through the Connecting Cave, you find yourself in Muraille Coast on the way to Ambrette Town.
Get the Coastal Pokédex
Go west and walk down the stairs. Sina and Dexio will appear and add the Coastal Kalos Pokédex to your Pokédex.
In the grass, you can find Spoink, Absol, Bagon, Drifloon, Mienfoo, Inkay, Seviper (Y only), and Zangoose (X only).
Go north from the Route 8 road sign and walk east along the narrow path. Check on the rock to find a hidden Super Potion.
Go west from there and go to the northwest corner of this area, then hop down the ledge. Then hop down the ledge on the left. Then hop down either of the two downward ledges. From there, go south, then use the ledge that goes to the right. You'll find an HP Up.
Use the ledge that goes to the right. Nearby you can see Rising Star Paulette, who has a level 19 Axew.
Go south through the grass near Paulette, then use the stairs to the right. You can see a big boulder here, but you'll have to come back later when you have a pokémon that knows Strength.
To the right of the stairs, there are some yellow flowers. Go south and you encounter Rising Star Rhys. He has a level 15 Pancham, a level 17 Goldeen, and a level 16 Skiddo.
Go south from the Rising Star and down some stairs. Go west to find Black Belt Cadoc. He has a level 20 Machop.
From the Black Belt, go to the southeast, and go south through some grass. Continue south and you'll see a little ledge going east toward some rocks sticking up out of a shallow pit. Skip the first little ledge and go south to find another ledge. Hop east from it to reach a Leaf Stone.
Now go back to the top of the pit and use the northern most little ledge to hop onto the rocks. Go south and hop off at any of the three ledges at the bottom. Continue walking south and you will arrive in Ambrette Town.