Magikarp
Boxing, by far.
bulbasaur is the easiest to level and is the best at fighting the gyms. i personally go for charmander because he is ultimately the best of the 3, but is the hardest to train. squirtle is suited for intermediate playing
the hardest Pokemon to find is regigigas you can only get him after finding all the other Pokemon and you can find him in the hippodow temple
train... train...TRAIN...
Train it as you train all pokemon.
latias
You an train Pokemon in the grass
Piplup: it is easiest to start off with since it evolves slowly so you can train it. Turtwig: it is in the middle Chimchar: it is hardest but it is the strongest (and also my favorite ^.^)
A fleeing legendary pokemon
Train at victory road
feebas
I personally like mudkip and Torchic. Treeko is my least favorite. Mudkip really helps you get past the gyms and isn't to hard to train. Torchic is good and it is the hardest to train, and Treeko is the easiest to train. It really depends on what type you like better. Hope this helps