After you pass through Paniola Town and Paniola Ranch, you head north to Route 5 on your way to Brooklet Hill.
The Trial Guide near the entrance of Route 5 asks you to defeat all the trainers in Route 5, then come back and talk to him.
Go north from that Trial Guide to find a Super Potion.
If you go into the grass to the right, there is a hidden Star Piece to the right, next to a big rock.
Go south from there and go up the ramp to reach a rocky ledge. Go north along the rocky area to find TM41 Torment. You can go to the left and jump down the one-way ledge to continue.
Go west from there and you can battle Pokémon Breeder Yuka. She has a level 16 Morelull and a level 16 Ledyba. You get 640 Pokédollars for winning.
You can't go farther north, because a couple of Team Skull Grunts won't let you enter the grass there. Go south and you can battle the two kids to the left. They are Twins Isa and Nico. They have a level 15 Cottonee and a level 15 Petilil that you battle simultaneously with two of your pokémon. You get 360 Pokédollars for winning.
Go west from the twins. You find Hau, who has just lost against Gladion. Gladion challenges you to a battle. Team Skull Gladion has a level 17 Zorua (disguised as a Zubat), a level 17 Zubat, and a level 18 Type: Null. You get 680 Pokédollars for winning.
Afterward, there is a cutscene, and Hau gives you three Revives.
Go southwest, then go north through the grass to find a Revive.
Go back through the grass, then go west. To the north, you can battle Pokémon Breeder Cory, who has a level 16 Paras and a level 16 Spinarak. You get 640 Pokédollars for winning.
Go north from there to reach the Pokémon Center. You can go east from the Pokémon Center to battle Rising Star Duo Lauren and Justin. They have a level 17 Rufflet and Level 17 Vullaby. You get 1632 Pokédollars for winning.
Route 5 Pokémon Center
Go into the Route 5 Pokémon Center. Talk to the guy holding the fishing rod to get a Super Potion.
Talk to the guy in green, and if you have a Lillipup, you can trade it to him to get a Noibat named Noinoi. Lillipup can be found in the grass near this Pokémon Center. Kihei's Noibat is holding Bright Powder, which reduces opponents' accuracy. Noibat will evolve at level 48.
Talk to the researcher to the left and he asks you to catch a Corsola and show him your Pokédex afterward. He will pay you if you do.
When you are ready, go outside and go into the cave to the left to enter Brooklet Hill.