Okay, time to set a few things straight in this conversation gone awry about EVs. Here is a link to a great guide written by Synchronize about Effort Values that you both should read:
https://www.pkmncommunity.com/showthread.php?t=72415
It is actually the third guide listed, but the first two are definitely good reads as you make your way down.
Essentially, an Effort Value is a number that is attached to EVERY Poke in the game. Every time any Poke particpates in a battle against another Poke, and defeats it, it will earn the EV points that particular Poke has (i.e. Skarmory yields 2 Def EVs). A Poke can learn a max of 510 EV points, and can only learn 255 EV points in any one stat. That means you can max only two stats on a particular Poke.
How EV points work is that for every 4 EV points a Poke earns, it increases that stat by 1 point when you level up. So, battling two Skarmory will give your Poke 4 Def EVs, and then you level up, its Def stat will increase by one. So, as you can see, you need to make sure that the EV points your Poke learns should ALWAYS be divisible by 4. That means maxing out a stat at 255 is wasting 3 points that could be used somewhere else. To fix that, I always only max to 252 in two stats (which you should only do in certain cases) and then I have six remaining points, four of which I can put in another stat.
As it was explained before, Pokerus double the amount of EVs your Poke can learn. That means, when it battles that Skarmory, it will get FOUR Def EVs instead of two. Have it hold the Macho Brace and it will double again, earning EIGHT Def EVs. So hopefully now you are beginning to see how valuable the Pokerus is and how envious I am of you. LOL
Also, keep in mind that whenever you catch a wild Poke or breed a baby Poke, its EVs will ALWAYS be at zero. It is not necessary to have to start EV training a Poke at Lv5. You can EV train them at any level, you can even EV train the Legendaries. Don't forget that earning EV points will only manifest themselves when you level up, so when you reach Lv100, you are unable to EV train anymore. Some claim that there is a trick to that, but since I haven't tested it yet, I am leery to accept it.
Beldum is not considered Legendary and can breed with Ditto. Since it is genderless, it will take at least twice as long as it does getting an egg otherwise, but you will get one. Be patient. Also, you destroyed Stephen's Metagross because it is a crappy AI Poke that hasn't been EV trained and does not have a beneficial moveset. Keep in mind that Blaziken cannot OHKO a trained Metagross with STAB Flamethrower, but Metagross can OHKO a trained Blaziken with Earthquake. That is why most Blaziken movesets suggest Fire Blast, or even Overheat, over Flamethrower.
Suggestions in
bold:
Blaziken
Hasty Nature (+Spd, -Def)
EV Focus: Atk, Spd, SAtk
Always remember that EVs should be used to accentuate a Poke's strength, not attempt to cover a weakness. Putting EVs into Def or SDef won't help nearly as much as putting them into Atk or Spd. Since Blaziken's special movepool sucks, it is always better to focus on physical attacks and then carry a Fire move as a STAB secondary move. Fire-types in general are meh. Swampert owns all. BTW - always avoid neutral natures. They offer no benefit whatsoever.
Gardevoir
Modest Nature (+SAtk, -Atk)
EV focus: HP, Def, SAtk, and a little Spd
And just after I say don't use EVs to cover a weakness, I present you with an exception. Giving Gardevoir some Def love actually does prevent it being OHKO'ed by a physical attack, assuring you at least two attacks (depending on how fast your Gardevoir is).
Glalie
Nature: Gentle
EV Focus: Defense and Spe. Atk
Don't use Glalie. Seriously. Walrien, Jynx, Lapras, and others are better alternatives.
Metagross
Adamant Nature (+Atk, -SAtk)
EV Focus: Atk, Max Def, Spd, a little HP
A STAB Meteor Mash can do as much damage as Psychic can, with its base Atk of 135 (along with some Atk EVs). Again, accentuate its strenghts (Atk, Def) instead of its weaknesses (SAtk, SDef). You don't want to keep Metagross in against its weakness anyway. That is what switching out is for.
About training your Pokes quickly. What I have done is added 19 Secret Bases on my Emerald cart, by mixing records with my Ruby cart that I have restarted many times. I restart a game on Ruby, play to the point where I can add a Secret Base, and then trade over Pokes from my Emerald to Ruby (more on that in a minute) and then mix records. After that I restart Ruby and repeat.
Why the hell would I do this, you ask? That is because I can fully EV train a team of Pokes rather quickly. Here is how it works. I have caught/bred six Pokes that will give me 3 EV points in a particular stat every time I battle them. They are:
Clefable - 3 HP EVs
Shiftry - 3 Atk EVs
Golem - 3 Def EVs
Beautifly - 3 SAtk EVs
Dustox - 3 SDef EVs
Raichu - 3 Spd EVs
I chose these Pokes because they are the quickest to acquire. I then remove all attacking move, via the Move Tutor. It is cheap, I know, but I want to train in the quickest way possible. Then I trade them to my Ruby cart and mix records. Now, when I enter that Secret Base, I can battle six Pokes that give me 3 EV points each, for a total of 18 EV points. Now, since I will typically have my target Poke hold the Macho Brace, it will actually earn 6 EVs points per battle, or 36 EVs points total. So, after seven trips to the Secret Base, I will have maxed out the EVs for a particular stat. Just imagine now if you did it with Pokerus. 72 EV points total from one run. That is sick. Simple math reveals that battling three times will yield 216 EV points. THREE times. Sick, sick, sick. So every day, you can take a Poke and practically max out a target stat. That is why I have 18 bases (3 bases for each stat, each base with 6 of the aforementioned Pokes). Sure it takes time to set up, but the end result is that I can mass EV train Pokes in very little time. Don't forget that using the Exp Share will allow a Poke to earn EV points too, and they don't even have to participate in battle. A Poke with Pokerus and Exp Share will earn 6 EV points in my Secret Bases just by being in the party while my target Poke is doing all the battles. Now can you see why I am so envious? LOL
Outside of dedicating time to do that, or not having the hardware to do so (requires two games and two GBAs), you can still EV train naturally. After you have finished EV training and you want to level up quickly, the best way to do it is to battle the Weak5, or my favorite is battling Gabby the Reporter (only in Emerald). She can be found first on Route 111. After that she is found on Route 118. You can then find her on Route 120. What happens is that after each battle, she will switch to the next route, allowing you to continually battle her without having to wait for her to want to. Also, after you battle her enough, she will stay on Route 111, allowing you to battle her quicker without having to Fly to the other routes. This is beneficial because you can earn Exp Points quickly, and you can quit at any time. If you don't have Emerald, then just stick with the Weak5.