After you make it through the Fiery Path and the northern half of Route 112, you reach Route 113.
In this route, you can find Skarmory and Spinda. In Ruby and Sapphire, you can also find Sandshrew. In Emerald, you can find Slugma.
Explore the Route
Go west. Eventually you find Youngster Neal to the north. He has a Trapinch and Linoone.
If you go east from Neal, you can hop down and find a hidden Ether and a Super Repel on the lower ledge. In Emerald, you can also find a hidden Nugget there.
North of Neal, Ninja Boy Lao is hiding under a pile of ash. He has four Koffings.
To the west, Parasol Lady Madeline has a Numel.
West of her, there are Twins Tori & Tia, who have two Whismurs.
If you go north and east from the twins, you can go south to get a Max Ether.
To the west, you find the Glass Workshop. Talk to the man there to get the Soot Sack. It allows you to collect volcanic ash by walking through the grass in this route. Then you can bring the ash to the Glass Workshop to get flutes. Different types of flutes have different effects, such as increasing wild pokémon encounter rate or waking up a sleeping pokémon during battle.
To the west of the Glass Workshop, Ninja Boy Lung is hiding behind some ash. He has a Nincada and Ninjask.
To the west, Youngster Dillon has an Aron.
North of Dillon, there is a pile of ash that has a hidden TM32 Double Team in it.
In Emerald, you can find a Hyper Potion west of there.
Go west to reach Fallarbor Town.