Pokémon FireRed and LeafGreen/Route 8

Route 8 usually leads directly to Saffron City, but once again, the direct passage ahead of you is blocked, forcing you to find an alternate way. No problem. Just go into the small cottage in the northwest and you will discover an underground passage that leads to Route 7, which in turn connects to Celadon City. But before you can get there, you need to fight a bunch of trainers that block your way.

To limit trainer battles to one, take on the easternmost girl, then go along the trees out of the sight of the old man, head across the field with cut, time the bike riders to skip them, and continue along the ledges. Head far north all the way to the house on the east side to avoid the last trainer.

Items
Rawst Berry (Hidden in one of the empty grass patches, top right corner)

Lum Berry (Hidden in empty grass patch, top left)

Leppa Berry (Hidden in empty grass patch, lower right)