In this city:
Upon entering, talk to the boy to the left. He will give you TM41 Torment. Afterwards, check the mushrooms behind him to obtain a Tiny Mushroom.
Go in between the two houses and pick up the Ether at the back. The second house is a Boutique.
Follow the path and you will find the Pokémon Center. Talk to Mr. Bonding in the corner and he will give you the Encounter Power. It increases the chance of encountering wild Pokémon. The Poké Mart in this town sells EV boosting Vitamins.
To the right of the Pokémon Center is a guy that wants to see a Pokémon that is smaller than 12 inches. Flabébé would be your best choice as it is one of the smallest Pokémon. Show him what he asks for and he will give you a Poké Doll.
Head to the north and cross the bridge. You cannot surf on the waters but you can go fishing. There are wild Pokémon you may not have seen yet in the pond. The first building you will see upon crossing the bridge is the Laverre City Gym.
In the house to the right is a person that will teach a starter Pokémon a Pledge move. There is the Fire Pledge, Grass Pledge and Water Pledge. These moves can be used in combos during Double or Triple battles.
Exit the house and head to far left. In the lower left corner is an Ultra Ball hidden in the grass. Take the stairs up then head left again, talk to the hex maniac and she will give you a Gengarite.
In the house behind the hex maniac is where the head of the Kalos Pokémon Fan Club is. He is the old man at the back. If the leading Pokémon in your party has a maxed out EV, he will give you an Effort Ribbon for you to give to your Pokémon. The lady in front will tell you how close you are with your Pokémon.
The house to the right of this one has another hex maniac that can tell you who you’re the Pokémon in your party was during in your previous Gym Battles.
Exit and ignore the stairs going up for now, it leads to the Pokéball Factory. Keep on going to the right and check the mushrooms for a Leaf Stone. The building here is another Café, where you get to view Pokémon not yet seen in your Pokedex, for a price.
The girl in front of the Café is similar the the guy near the gate earlier. She will be asking for a Pokémon that is larger than 9’10”. The best choices for these are the long Pokémon, such as Gyarados, Onix and Steelix,. She will also give you a Poké Doll if you are able to give her what she is looking for.
With that there is nothing else to do in the city, head back and challenge the Laverre City Gym.