[Soulcleaver]

1. Gym : Route 22 : Progress City
2. Gym : Route 47 : Tulip City
3. Gym : Route 72 : Dragonfly City
4. Gym : Route 97 : Death Stalker City
5. Gym : Route 123 : Ocean Breeze City
6. Gym : Route 147 : Iceberg City
7. Gym : Route 183 : Fortified City
8. Gym : Route 213 : Glyptodon City
9. Gym : Route 240 : Volcano City
10. Gym : Route 269 : Power Center City
11. Gym : Route 294 : Star Light City
12. Gym : Route 321 : Martial City
13. Gym : Route 350 : Ferrous City 
14. Gym : Route 379 : Sakura City
15. Gym : Route 401 : Airborne City
16. Gym : Route 429 : Nightmare City
17. Gym : Route 457 : Sky Dragon City
18. Gym : Route 486 : Nebulous City
19. Gym : Route 519 : Grand Monster Capital
20. Gym : Route 313 : Path of Tears 
21. Gym : Route 519 : Grand Monster Capital (School Building)

[ERDarky1]

I made this video just so that people can get to the gym once you arrive in the city without battling any npc's (in the city)
https://www.youtube.com/watch?v=kQQA3u10qsY
hope this helps :)