After you help Dawn or Lucas defeat a pair of Team Galactic Grunts in Jubilife City, you head north to Route 204.
Get a Paralyze Heal
If you didn't get it earlier, go northeast through the grass, and you will find a Paralyze Heal.
Catch Pokémon
In Route 204, you can catch Bidoof, Budew, Kricketot (only at morning and at night), Shinx, Starly, and (only at night) Zubat, and you can use the Old Rod to catch Magikarp.
Trainer Battles
Go north along the route and you can battle Lass Sarah (if you haven't already), who has a level 7 Bidoof. You get 392 Pokédollars for winning.
To the west, you can battle Youngster Tyler (if you haven't already), who has a level 5 Magikarp and a level 5 Starly. You get 380 Pokédollars for winning.
North of there, you can battle Lass Samantha (if you haven't already), who has a level 7 Budew. You get 392 Pokédollars for winning.
Go north from there to reach Ravaged Path.
Catch More Pokémon
In Ravaged Path, you can catch Geodude, Psyduck, and Zubat, and you can use the Old Rod to catch Magikarp.
Get an Antidote
Go north in the cave to find an Antidote.
Get TM39 Rock Tomb
Go north and check on the rock on the left to break it with Rock Smash. Then go west and you will find a TM39 Rock Tomb.
Route 204, Part 2
Go to the east side of the cave and break the rocks there, then go east and then south at the sunlight to go back outside.
Go north up the stairs and you can battle Aroma Lady Teighler, who has a level 7 Budew and a level 7 Cherubi. You get 504 Pokédollars for winning.
To the southeast, there is an Awakening.
Go north through the grass and you can battle Bug Catcher Brandon, who has a level 7 Kricketot and a level 7 Wurmple. You get 392 Pokédollars for winning.
To the northwest, you will battle Twins Liv and Liz. They have two level 9 Pachirisu. You get 1152 Pokédollars for winning.
To the west, go through the narrow path between the fences to find TM09 Bullet Seed behind a tree.
Then go back east through the narrow path between the fences, and go north from there to reach Floaroma Town.