You cannot get the Legendary Dogs (or Beasts such as Raikou, Suicune and Entei) in Ruby without either trading for them or cheating for them because they are not available in the wild in Ruby in any way, shape or form.
But you can catch it in Pokemon Ruby Destiny-Reign of Legends. But in the original Ruby or Sapphire you can't get it.
Chat with our AI personalities
You can find Lugia, the legendary dogs/ Suicune, Enti, and Raichu, and I think Ho-Ho
Three legendary dogs, Ho-oh Lugia and a dragon type pokemon.
Wat do u think BUDDY? By the way, they are the legendary cats, not dogs. The Pokemon Company revealed that Raikou is a tiger, Entei is a lion, and Suicune is a cheetah.
Entei (Fire), Raikou (Electric) and Suicune (Water)
I don't think you can refight any legendary Pokemon except the wandering dogs.