After you go north through Route 210 and find your path blocked by some Psyducks, you go east to Route 215.
In Route 215, you can catch Abra, Geodude, Kadabra, Kricketune, and Ponyta.
Battle Trainers and Find Items
Go east, then up the stairs, then north up the bridge, then down the northern stairs.
There is a Honey Tree to the north.
To the south, you battle Ruin Maniac Calvin, who has a level 21 Bronzor and a level 23 Shieldon. You get 1380 Pokédollars for winning.
To the east, there is an Ether.
Go east and south from there, then go east up the stairs and talk to the Black Belt to get some TM66s, which teach Payback.
Go east, then north up the bridge. There is a hidden jar of Honey on the rightmost flower at the end of this bridge.
Go west across the bridge, then north down the stairs. To the southeast, you can battle Black Belt Derek, who has a level 25 Croagunk. You get 900 Pokédollars for winning.
Go northeast and cut the tree, and go east to battle Black Belt Gregory, who has a level 23 Meditite, a level 22 Machop, and a level 21 Meditite. You get 756 Pokédollars for winning.
Near the Black Belt, there is a Fist Plate.
Go south down the ledge, and if you keep going south, there is a tree to the southeast that you can cut to reach some berry trees to the east.
Go back the way you came and go up the stairs to the east. Go south to get a Guard Spec.
Go north, and go down the northern stairs. Keep going north, and go to the tree to the northeast that you can cut down. There is a hidden Hyper Potion on the flower north of the tree.
To the east, you can battle a Black Belt who is behind a tree. Black Belt Nathaniel has a level 21 Croagunk, a level 22 Machop, and a level 23 Meditite. You get 792 Pokédollars for winning.
To the northeast, there is a hidden bottle of Zinc.
To the south, there are trees you can cut down to reach TM34 Shock Wave.
Southwest of there, you can jump down from the ledge to reach a Full Heal.
Go east from there and there are two Ace Trainers. You can either battle them separately talking to them from the side, or battle them at the same time by walking between them.
The southern trainer is Ace Trainer Dennis, who has a level 23 Monferno and a level 23 Gyarados. You get 1656 Pokédollars for winning.
The northern trainer is Ace Trainer Maya, who has a level 23 Glameow and a level 23 Kadabra. You get 1656 Pokédollars for winning.
Go east and you find some berry trees.
Go east from there and you will reach Veilstone City.