Pokemon Pearl advice

Lopunny!
Best Pokedude ever!

But in all serious, I would add a Murkrow. They evolve into the awesome Kingkrow. Best pokemon ever.

 

I know I'm quoting myself, but I just realized that Lucario is a steel type, which is HORRIBLE in the metagame since Earthquake is ALWAYS in someone's team, and usually more than once.
Lucario has good type coverage offensively, but it is also idealistic. Works great against the computer, but any seasoned battler will use something a little more annoying, like status attacks and whatnot.

There's really only one good steel type and that is Skarmory.

Also, for your Infernape, Grass Knot or Hidden Power (grass) is a good choice.