Q&A for How to Beat the Elite Four on Ruby, Sapphire, or Emerald

Well, honestly, Wallace is easier than Steven. You only need a ludicolo/brelloom and magneton/raichu to defeat him, but make them at least of level 58, and milotic will be a problem so carry some revival herbs.

Train with them for a bit until they're a higher level. You could try as you are, but you'd have to be fairly lucky.

Not necessarily. Kyogre/Groudon will definitely have the strength, but not the levels, and might not mesh well with the balance of the team.

Go to Lilycove City and use Super Rod at the water. You will have 15% chance to encounter a level 25 - 30 Staryu and 85% chance to encounter a level 25 - 45 Wailmer.

It depends on which game you are playing. If you are playing the Ruby version, you can find Groudon in the Cave of Origin in Sootopolis City. You can find Kyogre in Sapphire in the Cave of Origin in the same place. If you want both, you would have to trade with someone generous or gullible.