huangover

This article will help you if you're just trying to learn the basics.

http://www.serebii.net/games/evs.shtml

You can buy the Power Items in the Obsidia Dept Store on one of the upper floors, can't remember which.

If you want Pokerus, I'd be glad to trade you something with it. Just remember that its contagiousness only lasts for a limited time (you can slow this by putting the affected Pokemon in the PC, or by having it spread to other members of your team).

As for helpful places to EV train:

Speed: Underground Railnet, if you haven't fixed it up already. The shadows on the ground are Woobat, which give 1 Speed each. If you enter from the Peridot Ward, there'll be 2 shadows right near the entrance, so you can just leave and come back to reset them. What I like to do for fast special/physical sweepers is to give my Pokemon a Power Lens/Bracer, then battle 32 Woobat (if you have Pokerus) to max out the preferred attacking stat. Then I'll give them the Power Anklet to finish up Speed training.

HP: If you choose not to renovate Azurine Island, this is a great place to train HP. Most Pokemon there will yield HP, but sometimes you'll run into a Golbat or whatever that yields Speed instead. If not Azurine Island, wild Audino are pretty common outside of Calcenon City, though you'll have to be careful as everything out there is Level 50+.

Attack/Special Attack: What I like to do is fight the Woobat mentioned above and then use the EV resetter in Peridot or the friendship berries from the Obsidia Dept Store to reset Speed EVs.

Defense: The Magcargo in the Rock Smash rocks in Pyrous Mt on Apophyll each yield 2 Defense EVs. They are Level 35. Watch out for the field effects.

Special Defense: If Reborn City has already been renovated, surfing in Azurine Lake will get you mostly Tentacool or Tentacruel, which give 1 Sp Def. However, Wingull gives you 1 Speed.

Remember that you can always keep track of how many/what EVs your Pokemon have on their summary pages.

Hope I helped