EV's and IV's don't relate to each other nor do they affect each other. The only thing that makes them similar is that they both affect a Pokemon's stat. Characteristics are based off a Pokemon's IV's. If you feed your Pokemon with that combo, it guarantees that it will have the maximum EV's it can have. (63) However, it doesn't guarantee that it will have a max stat, because you need to have a positive nature AND a perfect IV in that stat in order to guarantee that it will have a max stat. Here are some important things to know:
1. IV's range from 0-31 in each stat, and are "hidden" in the game. This means you can have up to 31 more points in one stat for anyone. A Gengar with a speed IV of 0 would have 31 less speed at Level 100 than a Gengar with speed IV of 31. IV's are set for a Pokemon.
2. EV's range from 0-255 in each stat, and a Pokemon can only have up to 510 EV's. EV's are also hidden in the game. Every 4 EV's in a stat raises that stat by 1. (This is why people normally have a spread of 252/252/4 EV's - Having 255 is useless and you might as well put the last 4 in another stat) EV's, unlike IV's, can be controlled with stat reducing berries (I'm not sure if they were released in the Dream World yet though).
3. Natures are probably more important than IV's. If you want a strong Pokemon, you need to make sure they have a beneficial nature. For example, a Timid (+ Speed, - Attack) Gengar with a mediocre speed IV will be better than a Brave Gengar (- Speed, + Attack) with a decent speed IV. Remember, natures increase the stat by a whole 10%, where as IV's can only increase a stat by 31 at most.
4. Notes for EV Training: Vitamins should always be used first, they increase a Pokemon's EV's by 10 for each vitamin and cap out at 100. Vitamins can only increase a Pokemon's EV's UP to 100, meaning if you have more than 100 EV's and you try to use vitamins, they will not work. Always use it before anything else because they give a free 100 EV's. If you have access to wings, they make things a lot easier since they just add 1 EV for each wing and are not capped out.
Basically, when training a Pokemon, you'll want to make sure it has a good nature and count your EV's right when EV Training. Once you get a hang of the game, you can try to go for better IV's (Such as RNGing, or abusing the Random Number Generator in the game to ensure you get a Pokemon with solid IV's / natures every time). Movesets are also really important in battling.
Hope this helps a bit!
