Lilycove City.
The third gym leader in Pokemon Sapphire is Wattson and he is located in Mauville City.
In Pokemon Ruby/Sapphire/Emerald you go to the PokeMart building in Lilycove city to try the lottery once a day. It depends on your Pokemon ID number. You get better chances of winning by trading Pokemon with various people. First Prize is a Master Ball.
In rustboro city its located towards the bottom left of the city.
In Pokemon Sapphire, Ruby and Emerald the 7th Gym that's located in Mossdeep City has Psychic type Pokemon.
Jubilife City is located in Sinnoh, not Hoenn. Since Pokemon Sapphire takes place in Hoenn, Jubilife City is not accesible. You can buy a copy of Diamond, Pearl or Platinum in which travel through Sinnoh.
Steven's home is located in Mossdeep City. It is northwest of the Pokemon Center.
The art muesum is located at Lilycove City, at the top left.
at the Pokemon lottery in jubilife city if your lottery number corresponds to the id of your Pokemon
Sootopalis City
Jublife city
Technically there's infinite master balls because you can win one from the lottery in lilycove city in the dept store.
The timer ball in Pokémon Sapphire is located in Rustboro City. You must go to Mauville and talk to a guy located in front of the tunnel, he will tell you this.