If you don't like playing the slots, the easiest way is to just buy the coins. That's expensive to do, though, so you can give one of your Pokemon an Amulet Coin, go west to Cycling Road, and rematch the trainers there for money.
If your not good at slots you can purchase coins instead.
The team rocket game centre (it costs 3,500 coins)
get 2800 coins for the game corner to trade you a dratini
At the celadon city game corner a man behind the counter in the game corner will give you coins.
It is found at the Celadon Game Corner and must be purchased for 4000 coins.
It can be bought for 4000 coins in the game corner shop in Celadon city.
To get TM35 - flamethrower in FireRed, you have to go to Celadon City and win it for prize coins at the casino. I think it costs 4000 prize coins, so you'll have to play at the casino a lot or waste a lot of money buying coins.
You buy shadow ball with coins at the game center in cleadon city.
In Pokemon firered you can't, but in Pokemon leafgreen you can get it then trade it to Pokemon firered.
There is no Pokemon convention in firered.
The Pokemon porygon is obtained at the game corner exchange in celadon city you must buy porygon using your game corner coins it is 9,999 coins. Afterward if you evolve it you can breed it to get more.
To get Pokemon firered on PC download a vba and Pokemon firered ROM