Pokémon Crystal/Exploring Route 31
The path splits to the east and west, with the east featuring tall grass and the west featuring a paved path. The paved path is currently blocked, so head into the grass instead.
At the end of the grass lies the entrance to the Dark Cave. While it could technically be navigated, doing so in the pitch black darkness would be difficult. Hang near the entrance to catch the Pokémon Geodude if desired, but don't let the dim light of the cavern entrance leave your screen to make getting back out easier. Check out the item ball by the entrance to gain a potion.
Head west to find a berry tree that grows confusing curing bitter berries.
Bug Catcher Wade Edit
Head down south of the ledge to encounter Bug Catcher Wade. Before starting this battle, consider putting a weaker Pokemon in front to gain some experience in this relatively easy battle. An antidote may come in handy during or following this battle.
Wade starts with a level 2 male Caterpie. It knows tackle. Defeat it to earn 22 exp. He follows it up with an identical Caterpie.
Following that is his ace, a level 3 male Weedle. It knows the move poison sting, so consider using a poison type such as your own Weedle if you have one to safely dispatch it. Defeat it to earn 33 exp.
It's followed by one last Pokémon, a level 2 male Caterpie. Beat it to earn 22 more exp and 32 . Talk to Wade again and he will ask for your phone number. Wade will call about bug catching contests, and will also call to offer you berries he found.
Continuing to Violet City Edit
Just south of Wade is a free pokéball. Head northwest to reach the gatehouse to Violet City, "The City of Nostalgic Scents".