Zoro and Chopper the first to join in each sea. Zoro being the swordsman/combatant and Chopper being the doctor
Both of their roles are related to helping Luffy fight. Zoro’s role to help during the fighting more while Chopper’s role is to help after the fighting more
Nami and Robin the second to join in each sea. Nami being the navigator and Robin the archeologist
Both of their roles being related to helping Luffy progress through the world. Nami helping out more island to island while Robin helps them get to the final island aka laugh tale
Usopp and Franky being the third to join in each sea. Usopp being the sniper and Franky the shipwright. While their jobs on the crew might not seem very connected their roles in general are
Usopp’s the sniper with Franky basically being a living gun. Franky is the shipwright but before he joined it was unofficially left to Usopp. Even now Usopp is the main one to help Franky. Both are also inventors in their own rights Usopp having his factory and Franky his workshop
Sanji and Brook being the last to join in each sea. Sanji being the cook and Brook the musician
Both coincidentally filling up the roles Luffy most wanted. Food and music might not seem all that connected on paper but they very much are even in real life. Both being very important to the human experience filling the body and soul
As for Jinbe the first and potentially last person to join depending on who you ask role wise isn’t very connected to Zoro or Chopper. As the helmsman his job is closer tied to Nami or Franky’s tbh
Tho while not job wise he is pretty much a fighting Japanese (Zoro) half animal man (Chopper). Tho that doesn’t mean much especially when they’re no newer members to compare with
