After you complete the Trial of Ilima in Verdant Cave, you look for Lillie in Route 3.
In Route 3, if a shadow flies over your head, you might get attacked by a flying pokémon.
In the northern part of the route, you can battle Rising Star Ian. He has a level 13 Psyduck. You get 624 Pokédollars for winning.
If you go through the grass near Ian, there is a Heal Ball to the right.
If you go up the southern part of the route, where some shadows of flying pokémon are going around, there is a Sharp Beak next to the rock if you go through the southernmost path.
At the top of the northernmost path, you can battle Rising Star Tatiana. She has a level 13 Petilil. You get 624 Pokédollars for winning.
At the top of the hill, you find a sign next to a cave entrance. It goes to Melemele Meadow. Go inside.
In the cave, you find Lillie, who is looking for Nebby.
First, go downward and follow the downward path until you find a Great Ball.
You can walk down into the flowers. You will encounter wild pokémon there. If you see sparkles in the flowers, check on them to get Nectar. Go to the left and go up the ramp to get the Net Ball on the ledge.
Optional: Seaward Cave
If you go downward through the flowers, you find a hole in the wall to the left. You can check on it to go in to Seaward Cave. You find an Escape Rope there. If you go farther downward, you find a Heal Ball next to a rock.
Go right from where you found the Heal Bell and go down some one-way ledges. Ignore the northern path for now, because it's blocked. At the end, you find a cave exit, but before you go through, go down and follow the path, and go down when the path splits and check on the rock to find a Star Piece. Then go back up and go left to find a Super Potion. Then go up and right from there to get a Never-Melt Ice.
Now go back the way you came and go downward when the path splits. Then go toward the right to reach the cave exit.
You will come out in Kala'e Bay. Go up to get a Net Ball.
Go back into the cave, then go down and left, and when the path splits, keep going left. Then at the next split, go upward and you will reach a ramp to the left. Go up the ramp, then go upward to find the hole that you can crawl through to return to Melemele Meadow.
Back in Melemele Meadow
Go up the path from where you got the Net Ball. Go left from the guy standing there and you will go down a one-way ledge.
Go to the left through the flowers and go up the ramp at the end. Nebby is to the left, so check on Nebby. You will go together back to Lillie, who heals up your pokémon. She also tells you that you can change Oricorio's form by feeding it Nectar.
When you leave the cave, Hau challenges you to a battle. He has a level 13 Pikachu and a level 14 starter (Rowlet if you chose Litten, Litten if you chose Popplio, or Popplio if you chose Rowlet). You get 280 Pokédollars if you win.
Afterward, Professor Kukui tells you that now that you have finished your trial, you need to battle Kahuna Hala to complete your grand trial.
Go in the direction that Kukui and Hau went, and you will find a bridge. Before you cross it, go to the right and talk to the man to get a Soothe Bell.
Now go to the left and then go down across the bridge. You can fight Rising Star Joshua, who has a level 13 Growlithe. You get 624 Pokédollars for winning.
Farther down the path, you find a Super Potion.
Go back upward, across the bridge, and talk to the guy to the left. You can battle him if you wish. He is Ace Trainer Makana, and he has a level 13 Rockruff and a level 14 Slowpoke. He uses Red Cards, which causes your pokémon to get switched out after attacking his pokémon. You get 952 Pokédollars for winning. He will also give you a Red Card after the battle.
Now go farther south. You will see some grass to the right. Beyond it, there are some berries. To the right of where you found the berries, there is a Nest Ball.
Go downward from the grass and talk to the guy. If you agree to help him, he asks you to catch a Rockruff in Ten Carat Hill and show him your Pokédex afterward. He will pay you if you do.
Then go south and you will reach Route 1. Go left from there and go up the stairs to reach Iki Town.