Outside Pinwheel Forest
Upon arrival in the area talk to the first girl you meet. It will give you TM 94 (Rock Smash) that serves to break small rocks on the road. You will find here Burgh and he will tell you to go to the forest. But before you go, we will fight and pick up some items. The woman before the grass is a trainer, but you need to talk to her to battle.
After the battle, she will heal your Pokemon, and every time you talk to her, will have restored your Pokemon. There are a variety of new pokes in the grass is a good source of experience. Below, there are two trainers.
Take the Great Ball more right and go down to face another trainer.
Take the antidote in the way and Battle against another trainer.
Climb the stairs and battle against two more trainers.
Once a day, you can break the larger stone with a Pokemon-type fighter. You will earn a Star Piece. Keep this to sell. Go down the stairs to the left to find a Netball. A Net Ball can capture the water type Pokemon and Pokemon-type insect easily. Go back to the left side of the route and get a Super Potion. Talk to the nurse to heal your Pokemon and head into the woods.
Inside Pinwheel Forest
Pinwheel Forest is full of Grass- and Bug-types, which can easily inflict status conditions. A Nurse will heal your Pokémon if you need it. Travel through the forest and battle many Trainers so you can chase Team Plasma. Most of the wild Pokémon in this area are about level 15-16, but they can be up to level 25 in the dark grass.
(trainer list incomplete)
After defeating Team Plasma Grunt #4, he will give you the Dragon Skull. Give this to Lenora and she will give you a Moon Stone. If you have Munna, then you can now evolve it. Now, head north towards the Skyarrow Bridge!
This bridge has some interesting camera animations as you walk across it towards Castelia City. You can get a Quick Claw in the bridge gate, which can sometimes allow slower Pokémon to attack first.