Do you know the news reporter gabby and her cameraman Ty well they go around the hoenn region searching for trainers you can battle these two infinite times have your level 10 Pokemon NOT participate in battle instead have it hold exp share then take care of the battle with your stronger Pokemon when your done you will notice your Pokemon has leveled up a few levels, you can make this even easier if its a Pokemon that was traded to you and try this at the elite four it will be level 30 by the time you finish!
Train a Vibrava to level 50 to get Vibrava train a Trapinch to level 35.
Train a Bagon to level 36 to get a shelgon.
Train wailmer to level 40.
give a sooth bellto rhyhorn and train to level 42
the price is a legendary Pokemon dialga at level 90 and the secret is train all of your Pokemon level 70 don't increas all of your Pokemon's level when its 70 you will never win train (ALL) of your Pokemon level (70) all you catch and received pokemons. (tips to train all of your Pokemon to level 70 battle the Pokemon league
Nowhere you must train a Bagon to level 30 to get Shelgon.
No if you want one you will need to trade a dratini from firered or leafgreen to sapphire then train it to level 55 OR purify the shadow dragonite in Pokemon xd gale of darkness then trade it to sapphire.
You can't find cradily you must train lileep to level 40.
You cannot catch glalie to get one you must train snorunt to level 40.
if you mean what Pokemon are easy to train, the easiest Pokemon to level up and stuff is your starter Pokemon. it's the same with Ruby and Sapphire, the start Pokemon always seems to level up quicker than caught Pokemon (at the beginning anyway) hope that helped :3 *Shi ~
train all your Pokemon equally
Train Surskit to level 25.