Run some drills
Your Pokémon begin working out to get ready for the upcoming Gym battle. You make a makeshift obstacle course for them to go through. Nidoran jumps through loops, Charmander decimates discuses, and Pidgeotto flies through loops. Your Pokémon feel a bit more confident in their skills, and in you.
After travelling for a bit, you finally arrive in Pewter City. You look over the city from above. Your first treat to civilization in awhile. Enjoy it while you can! You notice that the city seems to have a tint of grey… sort of bland. Nothing really stands out. You've got your Pokémon center, your Poke mart, your houses, gardens, and what not, but nothing special. I hear that there's a Pokémon Museum, though. But the building that really catches your eye is a building that appears to be completely constructed of boulders. The Pewter City Gym. It's humongous. You wonder why it would need to be that huge. But where you head to is up to you.
Your Options
Head to the Pokémon Center
Head to the Pokémon Market
Head to the Pokémon Museum
Head to the Pokémon Gym
Simply Explore the Sights