This will show, where you will be starting, when having different ranks.
Pirates
Rookie: Dawn Island
Pirate: Loguetown
Super Rookie: Jaya
Supernova: Sabaody Archipelago
Kaikyou: Fishmen Island
Tyrant: Karakuri Island
Shichibukai: Free Island
Yonkou: Foodvalten Island
Marines
Lieutenant: Shells Town
Captain: Loguetown
Commodore: Navarone Island
Rear Admiral: Sabaody Archipelago
Cipher Pol 9: Enies Lobby
Vice Admiral: Marineford
Admiral: Jungle Island
Fleet Admiral: Mariejois