there is no way
if you want to get 999 rare candies you need to get a gameshark.
Emerald = cannot find without gameshark Fire Red = safari zone (rare)
use cheats
The item duplication glitch (or Rare Candy glitch) can't be done in Pokemon FireRed version.
there is no way to get 999 rare candys without gameshark or action replay.
because once you use a gameshark it screws up your game thus making some features,like the TM case, not work.
The answer is use Pokemon fire red cheats.
GameShark SP, probably for Pokemon FireRed/LeafGreen
You can't buy rare candies in fire red. You can only find them, if you don't use cheats.
only by cheat code or game shark
well u can either trade with friends ALOT or hack