Part 4: Beat Wattson — Mauville City Gym, badge 3

Beat Wattson — Mauville City Gym, badge 3 opens 12 areas.

Where to go

1. Verdanturf Town

   Wild: Pikachu Lv 20

2. Fallarbor Town

   Wild: Pikachu Lv 20

3. Lavaridge Town

   Wild: Kecleon Lv 40, Togepi Lv 1, Wynaut Lv 1

4. Fiery Path

   Wild: Numel 60% · Lv 8, Grimer 35% · Lv 8, Koffing 35% · Lv 8, Slugma 5% · Lv 8

5. Jagged Pass

   Wild: Machop 65% · Lv 10, Spoink 35% · Lv 10

6. Meteor Falls

   Wild: Zubat 100% · Lv 9, Bagon 5% · Lv 20

7. Route 111

   Wild: Sandshrew 100% · Lv 11

8. Route 112

   Wild: Numel 65% · Lv 8, Machop 35% · Lv 8

9. Route 113

   Wild: Spinda 95% · Lv 9, Skarmory 5% · Lv 9

10. Route 114

    Wild: Swablu 66.7% · Lv 9, Lotad 33.3% · Lv 9, Seedot 33.3% · Lv 9

11. Route 115

    Wild: Swablu 100% · Lv 10

12. Route 117

    Wild: Oddish 37.5% · Lv 7, Zigzagoon 37.5% · Lv 7, Roselia 21.9% · Lv 7, Marill 3.1% · Lv 7

Everything you can have caught by this checkpoint · Open the interactive guide

It also doesn't say when 9 of its areas open up, so they are listed together in the last part rather than guessed into the story.