Sandgem Town is the second town you’ll encounter in the game, after Mom advises you to head there and find the professor.
Main Story Walkthrough
When you first arrive, you’ll encounter Rowan’s assistant who will ask you come to Rowan’s lab.
Head to Professor Rowan’s lab with them (left of the Pokémon Center). Talk to Rowan, who will not only let you keep your Pokémon but give you a Pokédex so you can go out and catch as many Pokémon as possible.
Exit the lab and talk to Rowan’s assistant, who will give you a tour of important landmarks. This includes the Pokémon Center and PokéMart.
After that, you’ll have to return to Twinleaf Town to let Mom know you’re leaving. Barry’s Mom will be at your house, and will entrust you with a parcel to deliver to him in Jubilife City.
The items in Sandgem Town can be purchased at the PokéMart. This early in the game, there isn’t a lot that’s useful you can buy, but there are at least a couple of things it’s handy to get before you continue on.
Other than the PokéMart and Pokémon Center, there are only two other locations in Sandgem Town.
The one on the bottom right is Dawn’s house. You can go in there to talk to her family.
To the left is another house with two people inside. They’ll advise you to use Pokémon Centers often and to avoid letting your Pokémon faint from having no HP left.