Pokémon Ruby and Sapphire/Route 123

Pokemon Found
Go down the path. If you have one Grass-Type Pokémon in your party, a girl will give you TM19 (Giga Drain). Grab the Berries here: Pecha, Sitrus, and Rawst, and follow the path to some more Leppa Berries. Then, hop off the ledge to the left to collect an Elixir.

Trainers
As you move to the left, on the low path, collect the Ultra Ball. If taking the high path, grab the Calcium. Either way, you'll end up at the Berry Master's House.

Pillage the nearby Berry Orchard for all kinds of Berries, including Qualot, Grepa, and Pomeg. Once you've looted his fields, go inside and talk to the Berry Master and his wife. The old man will randomly give you two Berries. Come back every day to get a new two. Talk to the Berry Master's wife. She will ask you for good sayings. Concoct a phrase and she will give you a Berry. Once you're done, fly back to Lilycove City.