^I'm sorry, but can you explain and IV's and EV's are? I don't understand.
IVs - that is,
Individual Values - are numbers between 0-31 that determine a Pokémon's HP, Speed, Attack, Defense, Sp. Attack, and Sp. Defense. As an example of how they work, using Attack as a basis, take two otherwise identical Axew and assign one an IV of 10 and the other an IV of 15 (we will assume they are the same nature for simplicity). The Axew with the IV of 15 is going to be a stronger Axew over time compared to the other Axew. When both fully evolve to Haxorus and are eventually at Lv.100, the IV of 15 will have a stronger Attack stat than the one with an IV of 10.
EVs - that is,
Effort Values - also attribute to a Pokémon's stats. However, these are something you have full control over. Let's take the same two Axew from above and assume they were trained differently. Battling a Pokémon will net all participants EVs; you can take an Axew and a Swoobat and have both participate in a battle with a Cubchoo and they will both gain EVs from the battle (Cubchoo nets one EV per participant). Pokémon with an Exp. Share will also gain EVs without battling. Now, let's forget about Swoobat. Let's take the two Axew from before and max out their stats. It is possible for the Axew with an IV of 10 (above) to train more on Attack EVs and thus become on par with, perhaps stronger than, the Axew with an IV of 15.
It should be noted that you cannot see IVs or EVs in-game. However, you ARE able to use an Action Replay code, plug your game in with the code activated, and use the status screen in conjunction with L+R to see exactly what your Pokémon's IVs are (they might look something like 15/10/9/14/18/17 when you write them side by side, read from top to bottom on-screen) as well as your Pokémon's EVs (which always start at 0 and go up based on battling experience - NOT based on experience points or Pokémon levels, and it should be noted a Pokémon can be Lv.100 without max. EVs).
One more note. There are
EV reducing berries. If you want to improve a Pokémon's EVs in one stat. but have maxed out your total EVs, feed it one of those six berries depending on what you want to reduce. It will lower the stat. by 10 EVs (or to 0 if already below 10), freeing up those EVs for you to train the Pokémon on opponents that will improve that EV upon defeat. The berry picker on Route 5 (B2/W2 only) will sell you berries five at a time every day, of different types. Join Avenue also expands its collection over time and it might be handy to have two berry shops as the selection will differ.
For a list of Pokémon to battle to gain certain EVs, see
here.
Cyclone