cheats
It is not possible to catch Celebi without a GSball because she is linked to it in an odd way.
Nope.
I don't think you can catch celebi at all in fire red. There is one way though bring your gameboy/ds with a wireless adapter to a Pokemon convention to get celebi.
There is no way You cant Celebi Whitout cheating Unless there is a NINTENDO EVENT.
The only way to catch Celebi in Pokemon FireRed Version was to get the special Pokemon from a event. The only other way would be to cheat using an action replay device with a code.
Currently, there is no way to get a official Celebi outside of Japan. However it may be possible to capture Celebi in future events.
trade it from someone who did cheat that way you didn't cheat
Sorry sweetie there's no way get Celebi on Ruby without cheats. The only way to have gotten Celebi was to go to a Nintendo event in the past where they were giving them away for free. Maybe there will be one in the new games coming up though, baby. ;)
While in the old Japanese Crystal version, you could obtain a GS ball for Celebi's shrine, they've yet to release any way in the newer versions to obtain a Celebi
With a master ball.
Cheat
Unfortunately it's not currently possible to get Celebi since Pokemon hasn't given him out since I believe the 10th Anniversary event if I recall correctly. So currently the only way to get Celebi is by trading.