Pokémon FireRed and LeafGreen/Route 3

At the entrance to Route 3 you will meet Prof. Oak's Aide, who will give you the Running Shoes. Now you'll be able to run fast by pressing. There is a Pokémon center at the end, so don't fret about returning back to Pewter City constantly. However, make sure you're well stocked up on potions before attempting Mt. Moon.

There is a salesman inside of the Pokémon Center, who will sell you a Magikarp for $500. Veterans of the Pokémon series will know this to be a ripoff because you can fish for them later in the game in almost any ocean area, so it isn't worth buying it.

Items

 * Oran Berry (Near Youngster Calvin)
 * Persim Berry: on the left side of the Pokémon Center in the middle of the rocks. Its spot is marked with a small dark dot.

Battles
In order to enter Mt. Moon, you need to battle a number of Pokémon trainers. Most of them can be avoided though.