Directly ahead is the town's Pokémon Centre. It would be rude not to visit it, right? When you're ready to move on, head left from the Pokémon Centre. After going up the steps, there are two houses you can visit. First, head for the corner below the houses, towards the left. There's an Artist here with a mid-life crisis or something.
What he wants to see is a Fire-type Tracksuit Jacket. You can buy one from the Hammerlocke boutique for 10,180 Poké Dollars. Put on the jacket and talk to him to receive TM78 Acrobatics. Next, go inside the house on the left. Speak to the man on the right to deliver the Old Letter from the girl in Hammerlocke. You'll receive a Choice Scarf.
Back outside, search the mushroom between the two houses for 2 Big Mushrooms. Then enter the house on the right. Chat to the woman in front to receive TM77 Hex (Sword) or TM42 Revenge. This is the TM from the Gym in the opposite version. Afterwards, go over to the right and speak to the breeder by the corner to trigger a battle.
Pokémon Breeder Elena
Dottler is the evolved form of Blipbug but it can further evolve into Orbeetle. This one is carrying an Eviolite, which boosts its defensive stats. It can also use Reflect and Light Screen to weaken your physical or special moves. If possible, use Fire, Flying, Rock or Ghost-types.
After the battle, you'll receive an Eviolite of your own.
This is a valuable hold item that increases a Pokémon's Defence and Special Defence stats by 50% in battle, but only if the Pokémon is capable of evolving and hasn't yet evolved. It doesn't work on the special Meowth, Pikachu or Eevee that can Gigantamax because they cannot evolve.
Exit the house and head right. Up ahead is a bridge leading to Ballonlea Stadium. For now, head south-east. Over on the right, pick up TM21 Rest, below the giant glowing mushrooms. Then head south. Search the small glowing red mushrooms to the right of the Pokémon Centre for a Balm Mushroom. If you continue south, there's a ledge that takes you back to the Pokémon Centre.
If you've got nothing else to do, head north into Ballonlea Stadium.