East of Mesagoza, you find South Province (Area Three), where Arven recommended that you go to investigate the Titans.
Get Picnic Ingredients
Near the west entrance of Mesagoza, you find a picnicker who gives you picnic ingredients and offers to have a picnic with you, which will heal up your Pokémon.
Northwestern Area
Northwest of the picnicker, there is a Revive.
Northwest of that, you can go down a ladder to an area down below. Go west from there to find another ladder, leading to an area farther down. The sign next to this ladder has a Gimmighoul hiding behind it that you can talk to.
In the northwest part of this lower area, you find a TM011 Water Pulse.
If you go east from the northwest part of the lower area, you can find a TM004 Agility.
Southeast of that, you can find a trainer that you can talk to if you want to battle. This is Miguel the Student, who has a level 12 Crabrawler. You get 624 Pokédollars for winning.
Main Path
If you go back to the picnicker at the gate to Mesagoza, you can go east and talk to the trainer to battle Martina the Student, who has a level 11 Arrokuda. You get 484 Pokédollars for winning.
When the path curves toward the northeast, you can optionally go southeast instead to find a ladder down into South Province (Area Five).
Otherwise, go northeast along the path until you can go east into a side path. It leads to a slope up to the top of a rocky hill, where you will find a TM093 Flash Cannon.
Northwest of that, you can talk to a trainer to battle Backpacker Samuel, who has a level 11 Starly. You get 660 Pokédollars for winning.
Keep going northeast along the path, and as you get close to the Pokémon Center, you will find a trainer that you can talk to, to battle Alicia the Musician, who has a level 11 Igglybuff. You get 1100 Pokédollars for winning.
You can go northwest from this trainer to find a TM031 Metal Claw at the end of the path.
You can try to use Koraidon/Miraidon to jump southwest from there onto the hill, where you will find an ominous black stake. You can check on it and say Yes if you want to pull it out. There is also an Exp Candy and a Luxury Ball here.
From the South Province (Area Three) Pokémon Center
Back at the South Province (Area Three) Pokémon Center, you can talk to the Pokémon League rep to get a Shell Bell if you have defeated at least 6 trainers in this area.
After you visit this Pokémon Center, you will get a call from Arven, who says that you won't have to try any difficult jumps or fall off of any cliffs to find the Titan.
You can go south from this Pokémon Center to explore a hill, where you can find a TM130 Helping Hand.
Higher up on this hill, you can talk to a trainer to battle Arnau the Poké Maniac, who has a level 12 Larvitar. You get 720 Pokédollars for winning.
If you go back to the Pokémon Center and go east along the main path, you can talk to the trainer to battle Severino the Office Worker, who has a level 17 Jigglypuff and a level 17 Skiddo that is holding Leftovers. You get 2720 Pokédollars for winning.
You can go north from this trainer to a narrow slope, and go northwest from there to find a TM005 Mud-Slap.
If you go back to where the trainer is, then go south, you will end up in South Province (Area Five). To stay in Area Three, you can go east.
East of the Office Worker
Northern Area East of the Office Worker
After you go through the narrow passageway east of the office worker, you can optionally go north down a narrow slope. In this area, you can find a TM017 Confuse Ray on top of a hill.
Keep going north from there to find a trainer that you can talk to, to battle Irene the Artist, who has a level 14 Fidough. You get 1400 Pokédollars for winning.
You can try to use Koraidon/Miraidon to jump northwest across the gap, where you will find a Max Potion.
Southeast of that, there are ruins with a couple of Gimmighouls on the walls that you can talk to.
Northeast of the ruins, you can talk to the trainer to battle Clara the Student, who has a level 17 Hoppip, a level 17 Salandit, and a level 17 Barboach. You get 2720 Pokédollars for winning.
North of the ruins, you can find a TM043 Fling.
East of that, you can talk to the trainer to battle Adrian the Office Worker, who has a level 15 Litleo. You get 1380 Pokédollars for winning.
In the northeast part of this area, there are two dead ends. In the westernmost one, you can find a TM055 Dig. In the easternmost one, you can find a TM006 Scary Face.
Main Path East of the Office Worker
If you go back to the office worker and go east along the main path, you can talk to a trainer to battle Benjamin the Student, who has a level 12 Sunkern and a level 12 Bonsly. You get 384 Pokédollars for winning.
Go northeast from the trainer to find a Gimmighoul at the base of a small tree that you can talk to.
North of that, there is a Full Heal.
If you back to the main path and go to the sign that points to Artazon, then look north, you see a low rounded rock. If you go to the right side of that rock, then turn around, you can see an item down below the rounded rock, in the cliff wall. You can fall down to that item to get a Rare Candy, then if you have Helping Functions enabled in your options, you can press Y to go back up. If not, you can go south to find a slope back up to the main path.
Back at the road sign that points to Artazon, you can see an area to the south, but for now, continue going northeast along the main path.
Near the top of the hill, you can go west along a ledge of rock to reach a Rare Candy.
Go east along the main path and you will find a picnicker. Talk to them to get sandwich ingredients and heal up your pokémon.
Go northeast from the picnicker and you can talk to the trainer to battle Laura the Artist, who has a level 12 Vivillon. You get 1200 Pokédollars for winning.
Northeast of the trainer, there is a watchtower. Check behind it to find a Heal Ball. Then climb the tower. It will be added to your Flying Taxi destinations. At the top of the tower, you will find a TM080 Metronome. There is also a Gimmighoul that you can try to catch.
You can try to use Koraidon/Miraidon to jump north off of the tower and get the Protein from the hill of rock below.
Go back down to the base of the tower. You can optionally go east from the tower to find a couple of items along a path that leads to a dead end.
Go back to the tower, and go west to return to the main path. Go east along the path and there is a Gimmighoul on a rock near a sign that you can talk to.
At this point, you have reached a crossroads where you can either go north, east, or southwest. If you look north, you will see a large Pokémon on the cliff wall. The path to Artazon is to the east, and the southwest path leads to an optional area.
Optional Southwest Area
If you go southwest along the path from the crossroads, you can check behind the tree on the left to find a Rare Candy.
Southwest of that, you find a Gimmighoul that you can talk to on a sign.
Near the sign, you can talk to the trainer to battle Noelia the Musician, who has a level 13 Toxel. You get 1300 Pokédollars for winning.
Southwest of the trainer, you find a TM004 Agility.
Go to the area north of that to find a Fresh Water and Ether.
Northwest of that, there is a Revive and Max Ether. Near those, you can talk to the trainer to battle Andrea the Model, who has a level 12 Flabébé. You get 1104 Pokédollars for winning.
Go southwest from that trainer to find a Moon Stone and a crystal for a Tera Raid.
Northwest of that, there is an Awakening, and you can return to the main path. Use the map to go back to the South Province (Area Three) Watchtower, then go southeast to the crossroads where you were before.
If you look north, you will see the Stony Cliff Titan. If you battle it, go south to return to the crossroads afterward.
Back to the Path
From the crossroads in the path, go southeast. You can talk to the trainer along the way to battle Cristina the Student, who has a level 13 Gastly and a level 13 Murkrow. You get 780 Pokédollars for winning.
Farther along this path, you can talk to the trainer to battle Amaia the Student, who has a level 13 Happiny. You get 416 Pokédollars for winning.
After you go farther east, you reach the Pokémon Center, and can go east into Artazon.