The Poké Mart has a few new items and even has someone new at the register. The person on the top register will sell you Air Mail for [pd]50 and Heal Balls for [pd]300. There isn’t really any reason you’d want Heal Balls, though, and you’re better off buying Poké Balls, which are now available from the other clerk for just [pd]200 each.
Other than that, there’s not really anything else to do here except return to Route 30 to the north. Make sure you’ve healed up your Pokémon, including your newly-caught ones, before proceeding!
[link to Route 30 (2nd Visit)]