65535 Gold:
At offset 0000 0040, change the current value (ex: 0C23) to FFFF

65535 Special coins:
At offset 0000 0044, change the current value (ex: 0C23) to FFFF

65535 Magic coins:
At offset 0000 0048, change the current value (ex: 0C23) to FFFF

You can try putting higher values by changing the next offsets, but the game has a limit and will put 1 if you go over it. Still, these numbers should be enough for a while and once you need more, just repeat.