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.
Don't waste time looking for both forms of Nidoran on Route 3; depending on your game, you only have a 1% chance of catching the rarer form. (Female in FireRed, Male in LeafGreen.) Your best bet to get both forms is to catch two males in FireRed, or two females in LeafGreen. On Route 5, you'll be able to trade the extra one with an NPC for the other gender.
|Fire Red||Level||Encounter Rate||Leaf Green||Level||Encounter Rate|
|#29 Nidoran♀||#32 Nidoran♂|
|Nidoqueen, Poison/Ground-type defense-orientated Pokémon.||Nidoking, which is Poison/Ground-type offense-orientated Pokémon.|
|Wigglytuff, but when evolved, it will not learn any more attacks by leveling up. Its stats and movepool aren't very impressive, so using it isn't recommendable.|
|Janice||Pidgey 9||Pidgey 9||144|
|Colton||Caterpie 10||Weedle 10||Caterpie 10||120|
|Ben||Rattata 11||Ekans 11||176|
|Greg||Weedle 9||Caterpie 9||Kakuna 9||Metapod 9||108|
|Sally||Rattata 10||Nidoran♀ 10||160|
|James||Caterpie 11||Metapod 11||132|