The Coumarine City Gym specializes in Grass-type Pokémon. Fire-type, Flying-type, Ice-type and Poison-type moves are recommended for this Gym. It would be best to have at least two of these types as there are some dual type Pokémon that are resistant to some of the Grass-type weakness. There are also Pokémon in this gym that have the ability Poison Point. It may cause poison when your Pokemon make contact with a Pokémon with this ability makes contact. Bringing Antidotes are recommended.
Climb the first rope up then swing to the right. The left area is a dead end. Battle the trainer to proceed.
Pokemon Ranger Chaise (Prize Money: P2,560)
Climb the rope up and proceed left twice. Ignore the rope in the middle as it leads to nowhere. You have the option of swinging to the right to battle a trainer but the way to the gym leader is to the left.
Pokemon Ranger Maurice (Prize Money: P2,320)
Use Fire on Ferroseed, Flying or Poison on Lombre and any of the super effective moves on Carnivine.
Swing to the left then down and left again for another battle.
Pokemon Ranger Brooke (Prize Money: P2,400)
It is best to attack Roselia with a Special move as Roselia may poison your Pokémon if you use Physical moves. Wormadam should be easy as it is really weak against both Fire and Flying-type moves.
Climb the rope up, left then up and end up at another split. There is nothing to the left so go to the right twice for another battle.
Pokemon Ranger Brooke (Prize Money: P2,400)
Climb up again and follow the path to the right to meet the Gym Leader.
Gym Leader Ramos (Prize Money: P5,440)
Jumpluff has a flying-type move so be careful with using a Fighting-type Pokémon against it. It should go down easily with an Ice-type move. Gogoat has Bulldoze, a move that is super effective against Fire-type and Flying-types so if ever you are using one of those, be sure to take this Pokémon down as soon as possible. The last Pokémon would be Weepinbell. As it is part Poison, Psychic type moves are also good against it.
After the battle, you will be awarded the Plant Badge. It allows you to use Fly outside of battle and makes Pokémon up to LV60 obey you even if they are traded. You will also recieve TM86 Grass Knot.
Take the slide to the right and exit the Gym. Head all the way south to continue to Route 13. On your way to the gate, you will receive a Holo Clip from Lysandre.
Enter the gate and you will see Sina and Dio. They will update your Pokédex to include the Mountain Kalos area.
Exit to proceed to Route 13.