Chapter 9: Thrifty Megamart
Use Charizard to fly back to Malie City. Heal up, then head left from the Pokemon Center back to Malie Garden. You'll walk in on Professor Kukui being harassed by a few Skull Grunts and Admin Guzma. He has a Lv. 30 Ariados and a Lv. 31 Golisopod. After winning, Kukui will give you a Z-Crstal for the final evolution of whatever starter you chose and take back his mask. Head back into the city and heal up if you need to. Head left and then south to arrive on Route 11.
Grab a Big Mushroom from the tall grass immediately to your left. There's a couple trainers that will double battle with you a little further down the route and TM74 - Gyro Ball is down the middle path. Keep moving right, there will be another trainer at the end of the fork. You'll come accross another trainer that is doing crunches shortly after and you'll find a Quick Ball near him. There's another Big Mushroom in the tall grass just south of this. When you arrive at the gate, the lady there will open it for you (assuming you passed the last trial).
If you head right a little on this Trail, Hapu will stop you and register Mudsdale to your Ride Pager. Use it to cross the rocky path and pickup the Burn Heal and Zygarde Cell on the other side. Hop off Mudsdale when you get to a narrow stretch that it can't fit through. You'll run into a trainer in a little meadow and an Elixir off a smaller pathway. You can go back and face another set of trainers in a double battle and pickup a Zygarde Cell now if you want, or you can just continue on this route. After the double battle, there's another trainer and a Hyper Potion near him in an Item Ball.
Head right a little from the sign on the route to get an X Attack and battle another trainer. From here you can head straight onto Route 13 or head South to the Secluded Shore to face a few more trainers. You can also pick up a Zygarde Cell on the south end of the beach and a number of pearls and big pearls by sniffing with Stoutland. Head to Route 13 when you're ready.
You'll be stopped by Hau as soon as you're on Route 13 and he'll give you Max Potion. Gladion will then show up and interupt the interaction. When the dialogue is over walk towards the oasis and pick up a Moon Stone. You can also pick up a Zygarde Cell right by a trailer to the south. South of town near the waterfront you can pick up a Guard Spec.. Head inside the trailer and talk to the punk and tell him you want to fight. He'll chicken out anyway and instead give you TM12 - Taunt. Head left to Tapu Village.
Head to the center of the village to meet up with Hau again. After healing up at the Pokemon Center, exit Tapu Village to the left. Continue north on Route 15 and enter the Aether House. Upon entering you'll immediately be challenged to a battle from a preschooler with an Elekid. You'll then be introduced to the next Trial Captain, Acerola. Exit the Aether House. You'll immediately have to stop Lillie from an attack by a Skull Thug. You should make quick work of his Drowzee. Lillie will then give you 5 Luxury Balls. Head back to Tapu Village on the right. Acerola will lead you down Route 14. Continue on this route past a fisherman trainer. There will be another trainer to defeat in front of the slope and you can pick up a Zygarde Cell on the right side of the beach next to the cliff. Then, head through the gates and talk to Acerola.
Thrifty Megamart Abandoned Site
Trial of Acerola
Acerola will explain that you'll use your Poké Finder for this trial. Enter the building whenever you're ready and the trial will begin. A conveyer belt will begin to move. Investigate and snap a picture of Gastly. You'll then have to battle it. A shopping cart will start to rattle when you move left. Investigate it and take a picture of the Haunter. You'll have to battle it as well. Follow the Pikachu again and you'll notice some levitating dolls. Investigate and snap a picture of the Gengar. You'll have to battle it too. Head north towards the doors and enter the room. Snap a picture of the Totem Mimikyu that is behind you.
After you take a picture of it, you'll begin a battle with the Totem Pokemon: a Lv. 33 Mimikyu. It'll summon Lv. 27 Haunter as it's ally. This Totem is very challenging as it has powerful moves that are likely able to OHKO many of your Pokemon. Keep in mind that the first time you hit Mimikyu, it won't deal damage due to it's ability, so don't use a Z-Move right away. Steel type work best against Ghost/Fairy, but Ghost moves are Super Effective as well (keep in mind this also works the other way). Once you beat the Totem Mimikyu, Acerola will award you with Ghostium Z and 10 Dusk Balls. Your trial will be complete.