How to Get Lots of Coins in 'Pokemon Crystal'
- 1). Travel to the Game Corner in Golden Rod City.
- 2). Walk up to the slot machines and press the "A" button to play. The slot machines are located on the back right side of the room on the second floor of the building.
- 3). Wait until you line up two "7"s, and then press and hold the "A" button. Hold the "A" button until a third "7" falls into place. Once it does, you will receive 300 coins. Repeat this process to quickly collect coins.
Source...