Like the main series of games, Pokémon Trading Card Game has got eight clubs, which are akin to gyms. In these clubs, you will face against several players before facing the Club Master. Defeating the Club Master gets you a special medal.

Grass Club
Location: Grass Club
Club Master: Nikki
Specialty: Grass-type
Reward: Grass Medal

After defeating all the members of the Grass Club, you will need to find Nikki within Ishihara's House. Talk to her and she'll return to the Grass Club.you will face Nikki who runs a deck based on Grass-type Pokémon. Nikki uses Venusaur's Energy Trans to make Exeggutor's Big Eggsplosion more powerful, typically

Flower Power Deck
Pokémon Trainers Energy
Card Quantity
4
3
2
4
3
2
4
3
Card Quantity
2
3
2
2
2
2
Card Quantity
18
4
Science Club
Location: Science Club
Club Master: Rick
Specialty: Grass-type
Reward: Science Medal

After defeating all the members of the Science Club, you will face Rick who runs a deck based on Poison-type Pokémon.

Wonders of Science Deck
Pokémon Trainers Energy
Card Quantity
4
3
4
3
2
1
1
2
Card Quantity
2
1
2
2
2
2
2
2
2
Card Quantity
15
8
Fire Club
Location: Fire Club
Club Master: Ken
Specialty: Fire-type
Reward: Fire Medal

After defeating all the members of the Fire Club, and collecting a total of at least 300 cards, you will face Ken who runs a deck based on Fire-type Pokémon.

Fire Charge Deck
Pokémon Trainers Energy
Card Quantity
4
3
2
3
1
1
2
2
Card Quantity
1
2
2
1
1
2
3
1
1
1
Card Quantity
21
4
Water Club
Location: Water Club
Club Master: Amy
Specialty: Water-type
Reward: Water Medal

After defeating all the members of the Water Club, you will face Amy who runs a deck based on Water-type Pokémon.

Rain Dancer Deck
Pokémon Trainers Energy
Card Quantity
4
3
2
3
2
4
3
2
Card Quantity
2
1
1
1
2
1
2
2
1
Card Quantity
24
Lightning Club
Location: Lightning Club
Club Master: Isaac
Specialty: Lightning-type
Reward: Lightning Medal

After defeating all the members of the Lightning Club, you will face Isaac who runs a deck based on Electric-type Pokémon.

Zapping Selfdestruct Deck
Pokémon Trainers Energy
Card Quantity
4
3
4
2
4
2
1
Card Quantity
1
2
2
4
1
4
Card Quantity
24
2
Psychic Club
Location: Psychic Club
Club Master: Murray
Specialty: Psychic-type
Reward: Psychic Medal

When you get to the Psychic Club, if you have managed to obtain at least 4 medals, you will face Isaac who runs a deck based on Psychic-type Pokémon.

Strange Psyshock Deck
Pokémon Trainers Energy
Card Quantity
4
3
2
2
3
3
2
Card Quantity
2
3
4
2
4
3
1
Card Quantity
22
Rock Club
Location: Rock Club
Club Master: Gene
Specialty: Fighting-type
Reward: Rock Medal

When you get to the Rock Club, you will face Gene who runs a deck based on Rock-type Pokémon.

Rock Crusher Deck
Pokémon Trainers Energy
Card Quantity
4
2
4
3
2
3
3
Card Quantity
2
1
2
2
1
2
2
1
Card Quantity
24
2
Fighting Club
Location: Fighting Club
Club Master: Gene
Specialty: Fighting-type
Reward: Fighting Medal

When you get to the Fighting Club, talk to Mitch. Then, after defeating all the members of the Fighting Club across the various clubs in the island, specifically Fire Club, Grass Club and Rock Club, you will face Mitch who runs a deck based on Fighting-type Pokémon.

First-Strike Deck
Pokémon Trainers Energy
Card Quantity
4
1
4
3
2
4
2
Card Quantity
4
2
2
2
3
2
Card Quantity
25