It depends on your starter pokemon.
If its a fire type than have an electric or grass type
If its a water type then have a fire type or a flying type
Ifits a grass type then have a water type
In Pokemon pearl you should raise a piplup, shinx, starly, riolu, the first form of rampardos and a gastly HAPPY TRAVELLING
you need the National pokedex and you need to defeat the Pokemon league
defeat the Pokemon league and then talk to prof Rowan and he should give you a poke radar. Then go to the patch of grass outside canalave city and use it. If there is a sparkly patch of grass go to it and you should find ditto.
Electric and ice Pokemon should do it.
After you defeat Wallace, head out to sea again and surf east until you reach Ever Grande City. Go up the waterfall and up the stairs into Victory Road. After you beat Victory Road, follow the path, and you should reach the Pokemon League.
probably at 100 cus he sucks
FireGrassWaterGhost or DarkElectricRock or Grond
all of them should be around level 50-60
i think you should train all of your Pokemon to at least lvl 55
If you can, its up near the Foght Area and the other two. If not, Migrate them from an Earlier Pokemon game (Defeat the Pokemon league and get the national deck to Migrate. To get the Pokemon you migrated, Go to Pal Park. Pal Park is at he very bottom where an "L" sticks out. At the tip of the ---- Part you should find it)
Pikachu
No. You should figure out what Pokemon types they have and build your team around that.