You'll be in the second part of Route 104. Head to the left and talk to the kid to receive TM49 Echoed Voice. Harvest the Pecha Berries(x3), Cherri Berry (x2) and Oran Berries(x2) outside the Pretty Petal Flower House and proceed inside.
Talk to the lady near the entrance to learn more about berries. Then, speak with the little girl to the right to receive a random berry. She'll give you random berries once a day so you can come back to her to receive a different berry daily. Next, talk to the young woman to the north to receive a Wailmer Pail. This will allow you water the planted berries.
Leave the house then proceed to the right. You'll find two trainers along the way.
Lady Cindy(Prize Money: P1,200)
Lass Haley (Prize Money: P128)
Now cross the walkway and you'll encounter twins that will challenge you to a double battle.
Twins Gina & Mia (Prize Money: P72)
Continue forth and after crossing the pool, head to the right. You can fight the fisherman there by talking to him, and you can also harvest Oran Berries(x8) and Cheri Berries (x4) from the trees there. Talk to the old lady as well to get a Chesto Berry.
Fisherman Ivan(Prize Money: P224
LV7 Magikarp(Water)
LV7 Magikarp(Water)
LV7 Magikarp(Water)
Head north to the right and walk around Rustoboro's fence. This will take you to a dead end with X Defense. Backtrack and enter Rustboro City.