Good Pokemon Strategies for Elite Four - Guide for Pokemon Ruby

some good pokemon for beating the elite four are:
Electrode knowing Thunder
                  Thunderbolt
                  Rollout
                 (your choice)
Hariyama knowing  Arm thrust
                  Vital Throw
                  Focus Punch
                 (your choice)
Mightyena knowing  Crunch
                   Bite
                   Thief
                  (your choice)
Glalie or Walrein knowing  Ice Beam
                           Blizzard
                          (your choice)
                          (your choice)

Ninetales knowing  Fire Blast
                   Flamethrower
                   Will o Wisp
                  (your choice)

For the first elite four member(Sidney) use Hariyama because fighting is good 
against dark. On Sid's Mightyena and Absol use Vital Throw and on everyone else use 
Focus Punch. Watch out for Absol because it knows Aerial Ace which shreds fighting 
tupe pokemon. 

For the second elite four member (Pheobe) use Mightyena and on everyone except 
Pheob's last Dusclops use Crunch. It will probably run out (trust me) and if that 
happens use Bite. On Pheobe's last Dusclops use Thief to steal its sitrus and then 
use Crunch, or Bite. 

For the third elite four member (Glacia) use your Ninetales's Fire Blast on the 
Glailies and use Hariyama's Vital Throw on the Walreins. Be patient. Glacia is the 
hardest of the elite four. 

Drake is the last of the elite four but he is the easiest. With your Glalie or 
Walrein (Glalie preferably) just keep using Blizzard on all his pokemon and if that 
runs out just use Ice Beam.

Now for the Champion, Steven. He is pretty easy but hard if you don't follow these 
insructions. On Steven's first pokemon Skarmory use Ninetales's Fire Blast. If your 
Ninetales is a high level it will knock out the Skarmory in one hit. After this 
Steven should change to Metagross. Keep using Fire Blast and you should be fine. If 
you run out use Ether. You shouldn't die. None of his other pokemon are steel type 
and your Ninetales should be in its reds but don't switch it out. Let it die and 
then choose your Ice pokemon. From then on use Ether on its Blizzard and Ice Beam 
and keep using those attacks. You should win.