Rocket’s Game Corner (the one in Leaf Green and Fire Red) is basically a “casino” in which you can play the slots and exchange your winnings for prizes. It also doubles as Team Rocket’s first base, until you defeat Giovanni once.
Several people have found this site by searching “Rocket’s game corner tricks,” and I decided to meet that search directly. There are several tips/tricks to Rocket’s game corner, and here they are.
In order to play, however, you need a coin case. Explore various buildings around town until you find what appears to be a restaurant of sorts. Talk to the old man in the back. You’ll receive a coin case from him.
Once you have a coin case, talk to the people playing in the game corner. Most of them will offer you some coins.
The slot machines are rigged; some of them have better odds than others. I’m not sure if the odds of the machines vary, but the machine farthest from the door on the second row from the right seems to have pretty good chances.
Once you have won a considerable amount of coins, you can go next door and exchange them for prizes. However, you can also just buy coins with regular money in the game corner. This is a much better alternative. If you have a prize in mind, go fight people in Pokemon battles; you get money this way, and you’ll have more fun. Once you have enough money, you can buy the necessary coins for the desired prize.
As I said in the intro, the game corner doubles as Team Rocket’s base. In order to infiltrate their base, you’ll need to walk up to the poster in the back, right-hand side of the building. Press “A” while standing in front of it, and a secret stairway to the base will appear.
Once you get in, it’s basically a wild goose chase to find various items that will do various things, until you find and fight Giovanni.
Rocket's Game Corner 