For Phebe, this girl is annoying!!! I just used my raquaza (you get it at sky pillar, a little east of Pecifialodge (Spelling?) and then north. Don't waste your Master ball, just make him sleep, get him down, then use ultra balls over and over.) Make sure he learns Crunch, and just crunch through all Phebe's pokemon, really not that hard if you have a Raquaza, but can prove to be a real pain in Ruby and Sapphire. Choose your moves wisely, Dusclops special skill, pressure, can lower your PP by one when you use a move.
For Glacia, This one isn't the hardest, if you have an electric (love electric!) then you can shock the fat evolution of Spheal (forgot what those were called, haven't played in forever, Sphelio I think, I have no clue!) with a Thunder! It might help if you have a pokemon with rain dance (can buy at lillycove city) so it never misses, like give it to Raquaza, and you can overite it afterwards. For Glaie, the ice ball things, use your Blaziken with Blaze kick and melt there body (if you melt the body, you'll just have eyes, and mouth and horns wtf?? lol) The final evolution of Spheal, forgot again what it is called, just use a thunder, or use a power move of Raquaza (even crunch will work, he's level 70 for cryin out loud!) Again, save your PP and don't waste a move, because ehters are limited, and tries at beating the elite four are not (as long as you are alive and have arms, lol).
For Drake, This one is EASY!!! Any number of things can kill this guy. First, get dragon claw (forget where to get it, check the TM/HM Walkthrough) and teach it to Raquaza, IT IS AN AWESOME MOVE FOR HIM!! NEVER DELETE IT!, Outrage is also a dragon move, but you can only attack twice or three time, and then you get confuse and your strategy falls apart. Just sweep through the whole thing with dragon claw (don't worry about PP) You could teach someone in your party Ice beam and freeze all of his dragons (cept final horsea evolution) This is especially useful for his Flygons, double super affective because it is Ground and Dragon. You don't need to worry about him, not even his Salamence, he's a goner if you have dragon claw or ice beam (check TM/HM walkthrough to see where to get ice beam).
For the last one, Walace, She can be a toughie for begginers, and you may be wondering "where is Steven? Why is Juan the leader of the Gym, and Walace the final Elite Four champion?" I have no idea why they did this, I thought it was pointless and stupid because Steven was so much cooler (and easier to beat, lol). This guy has tons of different pokemon. The first one, Wailern seems to have a lot of Hp, But two thunders (use rain dance first with Raquaza) and shock him with Manetric.(god I love that pokemon)! Next Tentacruel will come out, this guy is annoying andhas lots of Special Defense, go ahead and throw out another two thunders. Then the next is Ludicolo This might prove to be a difficult enemy, but if you teach Raquaza Aerial Ace (proves to be an actual good move for him) then you will kill him in a single swoosh. Next is Milotic, use yet another two thunders (make sure you save thunders for this guy) try not to use Raquaza, Milotic knows ice beam!! It also knows recover, but don't worry, it will go down. Gyrados is easy! One thunder and it's down for good!! now for the last one! Wishcash, just throw out your brellom and sweep'em with a solar beam! Now your finished! You won!! If you have any question don't bother to ask me here, or at firstname.lastname@example.org!
Note: You might wanna teach more than one pokemon thunder.
Note: Me and potato chips have always had a rivalry on cheathappens, ain't that right "shibby"