Chapter 1: Rustboro Gym
Exit the starting room and you'll run into your mom. Talk with her and head up the stairs. Check out the clock to set the time. Your mom will continue to blabber on for a while before you're finally allowed to leave the house and start your own Pokémon adventure. Head west and go into the house next door. May/Brendan's mom will tell you to go speak with your rival upstairs.
After a brief introduction, exit the house and head north to find Professor Birch being chased. Grab one of the Pokéballs from his bag and pick one to be your starting Pokemon.
Now battle with Poochyena to save Professor Birch. Head back to his lab where the journey begins. Here he will give you the Pokemon you selected earlier and send you off to Route 103 to find May/Brendan. Now equipped with your Pokémon, exit the lab and head north to Route 101.
Follow the route Oldale Town, where a representative from the PokéMart will appear. The NPC will give you 10 Potions. Heal your Pokémon here and then head north through the town to find Route 103. You'll find Brendan/May in the northernmost part of Route 103. Battle with him and head back south to Oldale Town. Continue south to find Brendan again. Follow him once more south and continue until Littleroot Town.
Continue south and go into Professor Birch's lab, where he will give you the Pokedex. After talking with Professor Birch, Brendan/May will give you some Pokeballs. Exit the house and head north, where your mom will speak with you. Continue north and Brendan will speak with you this time. He will give you the DexNav function for the PokeNav Plus. Continue follow Route 101 to find Brendan/May again.
Brendan/May teaches you how to sneak up on Pokemon. Do so and battle with the Poochyena. It may be wise to capture it using the Pokeballs from earlier so you have more Pokemon for fighting trainers and Gym Leaders. Now continue north to Oldale and head west to Route 102. Continue west to fight Youngster Calvin. Continue going west and fight the trainers along the way.
Near the end of Route 102, Brendan will appear for a moment and speak of the Detector Mode in the DexNav. Now continue west to reach Petalburg City. Head northwest to find a dialog outside of the city Gym. Wally will give you the PlayNav feature for the PokeNav Plus. Now head west to Route 104 and go north. Continue north and enter the Petalburg Woods.
Go northeast to find a researcher and a Team Aqua member that wants to ambush him. Battle with him and continue traveling through Petalburg Woods until you reach Route 104 again. Go east and continue by going north until you reach Rustboro City. Brendan/May will appear for a brief dialog. Head to the Rustboro Gym in the northeast of the city.
Gym #1 Rustboro Gym - Leader Roxanne
Rustboro Gym specializes in Rock type Pokémon, there's three trainers to defeat as well as the Gym Leader. As long as you've been battling trainers and any wild encounters your Pokémon should be at high enough levels to defeat the gym leader. If you picked Mudkip or Treecko (Water and Grass are our recommended types), you'll have the type advantage and Roxanne should be fairly easy to defeat. If you happened to catch a Poochyena that knowns Ice Fang, it'll also be very effective against rock types. If you let Geodude or Nosepass's health get too low, Roxanne may use potions to heal. Don't be hesitant to use potions/berries if necessary.
Roxanne will give you the Stone Badge and TM39 - Rock Tomb upon admitting defeat. You'll now also be able to use HM01 - Cut outside of battle and Pokémon Lv. 20 and below will obey you.
Continue to Chapter 2 Dewford Gym