You'll need a Coin Case, to be found in the restauraunt from the guy with the glasses along the main strip of buildings below where the Rocket Game Corner is. At the main desk in Game Corner (in the top left corner) you can buy 50 coins for 1000P. Unlike more recent titles, there is no 500 coins for 10000P option: you're stuck mashing the A-button unless you decide to play a few games. Make sure you look around everywhere on the ground in the Game Corner: there are plenty of free coins other people have dropped, to be found as you would with any other hidden item. Your Itemfinder won't pick them up, though.

The only game in the casino is a slot machine-style game. Insert however many coins you want (1, 2 or 3, which add more rows on the slots where you can win prizes) and try and line up the same picture. A triple 7 yields 300 coins, three BAR yield 100 coins, three Poliwag, Diglett, or Jigglypuff win 15 coins, and three cherries earn 8 coins. Go hog wild.

Location: Pewter City
Gym Leader: Brock
Specialty: Rock-type
Reward: Boulder Badge, TM39

Method:
The first gym is located in Pewter City and is a Rock-type Gym. It doesn't have much of a puzzle but there is a lone trainer who you must face before taking on Brock, the leader. This gym specialises in Rock-type Pokémon, and Brock will use the attack Rock Tomb to seriously wound Pokemon like Charmander, Beedrill, and Pidgeotto. Defeat Brock to earn the Boulder Badge, which lets you use Flash outside of battle, and TM39, Rock Tomb.

Location: Cerulean City
Gym Leader: Misty
Specialty: Water-type
Reward: Cascade Badge, TM03

Method:
Misty's gym is a straightforward path around a pool. You can avoid the first trainer but not the second. Misty uses the starfish Pokemon, Staryu and Starmie, which will try to smack you with confusion using their signature Water Pulse. They can also use Recover to heal. After you beat Misty, you receive the Cascade Badge, which makes traded Pokemon up to Level 30 obey you, and TM03, which contains the attack Water Pulse. You can also now use Cut outside of battle.

Location: Vermilion City
Gym Leader: Lt. Surge
Specialty: Electric-type
Reward: Thunder Badge, TM34

Method:
Before you can enter Vermilion City gym you must use Cut to clear the tree blocking the path. Once inside, prepare to check each garbage can until you find both switches to open the electric door. The second switch is always beside the first one, but if you find the wrong one the locks reset. Lt. Surge boasts a Raichu which can hit with the move Shock Wave, a fairly strong Electric-type attack that never misses. Ground-type Pokemon like Sandshrew and Diglett cannot be affected by this move, or any other Electric-type move. The prizes for this match are the Thunder Badge and TM34 Shock Wave. You can also now use Fly outside of battle.

Location: Celadon City
Gym Leader: Erika
Specialty: Grass-type
Reward: Rainbow Badge, TM19

Method:
Erika's gym requires Cut to navigate! Her Pokemon use the self-healing attack Giga Drain, which is also handed out via TM19 once the match is won. Also given to you are the Rainbow Badge, which makes any traded Pokemon up to Level 50 obey, and the ability to use Strength outside of battle.

Location: Fuchsia City
Gym Leader: Koga
Specialty: Poison-type
Reward: Soul Badge, TM06

Method:
The fifth Pokemon gym is a maze of invisible walls. The lighter tiles are actually invisible walls you must travel through to find Koga, the Gym Leader. The gym trainers are peculiar, using a mix of Ground, Psychic, and Poison-types. Koga's team however only uses Poison-types. While Muk can be hit with Ground-type moves, Koga's other Pokemon can't as they have the Levitate ability. Koga's Pokemon use a move called Toxic which causes a unique type of poisoning where damage exponentially increases each turn. The prize for this match is TM06 Toxic as well as the Soul Badge. After this match you can use Surf, which can be found in the Safari Zone.

Location: Saffron City
Gym Leader: Sabrina
Specialty: Psychic-type
Reward: Marsh Badge, TM04

Method:
Only accessible after the Rockets have been defeated, Sabrina's gym is a network of warp panels. Not all the trainers have to be fought, but many of them do in order to reach all these panels. Sabrina's team itself uses three pure Psychic-types and a Bug/Poison-type, Venomoth. Kadabra and Alakazam both have bad defenses so try to use attacks that fall under the physical type categories. Be careful though as they can do significant damage with their high Special Attack. As a reward for winning you get the Marsh Badge, while makes any Pokemon up to Level 70 obey you and lets you use the move Rock Smash outside of battle. The TM prize for this match is TM04 Calm Mind, a move which increases Special Attack and Special Defense one stage.

Location: Cinnabar Island
Gym Leader: Blaine
Specialty: Fire-type
Reward: Volcano Badge, TM38

Method:
After finding the hidden key to the Cinnabar Gym in Cinnabar Mansion, you'll be able to take a crack at Blaine's Fire-type Pokemon Gym. Each room has a quiz machine that asks you a question. If you answer it wrong or don't want to do it at all, you'll have to fight the trainer to open the door. Blaine uses several strong Fire-types that know the move Fire Blast. The prize for this match is TM38 Fire Blast, inflicts massive damage and can burn your Pokemon, and the penultimate Volcano Badge, which allows you to use Waterfall outside of battle.

Location: Viridian City
Gym Leader: Giovanni
Specialty: Ground-type
Reward: Earth Badge, TM26

Method:
After you have collected the seven other Badges and completed the quest in the Sevii Islands, the word is that Viridian City's Gym Leader has returned, and who should it be but the Team Rocket Boss Giovanni. The spinning tile maze here is similar to the one in the Celadon City Rocket Hideout. Giovanni's team now uses only Ground-types, and powerful ones to boot. When you defeat him you earn the Earth Badge, which allows you to control a Pokemon at any Level, as well as access to the Indigo Plateau west of Viridian City. You also get the TM for the strong Ground-type move Earthquake.