Simple, beat the champion in the Pokemon league.
p.s. The Pokemon league is tough, stock up on max potions,full restores,revives and
elixers and ethers if you use to many moves.
Train ur Poke'mon team and fight till u win
YES, YOU DUMMY!(after you defeat the Pokemon League and get the Ruby/Sapphire.)
The Pokemon League
On Ever Grande City
go to the Pokemon league and win. then get 60 Pokemon and go to oak and get natl. Dex then go to one island get ruby go to Cello and give him it he will give you it.
you only have to beat the elite 4 on Pokemon fire red not ruby
Through victory road.
To win the Pokemon league you have to have strong Pokemon that are at least level 60 or higher. I won by using legendary Pokemon( but that was me :P)
skill
Groudon. That's it.
You get your first Pokemon, then warp back there after beating the Pokemon league.
You can get ditto in Pokemon ruby by beating the Pokemon league then going to the cave the fossil maniac is digging he will be finished digging and he will say to be careful that there are Pokemon in there the Pokemon in there are ditto.