Zoro is the vice captain, they together shoulder the whole crew, there is chemistry for sure here.
Sanji is a bit the same, part if the M3, share the responsibility of the crew safety too to an extent.
Jinbe.. I don't see great interactions here. For sure below Zoro and Sanji at least.
Usopp. He is Luffy's bro, at least in the pre time skip they were together in a lot of gags, Usopp is easygoing and moronic like Luffy and unlike Zoro and Sanji (and others).
Chopper. Not at the lvl of Usopp but for sure in their free time (gags on the ship at least) Luffy spent time with Chopper too.
Brook. Moron like Luffy too, can be ascribed to the above group to a degree as well for me.
Nami. Lot of gags here too, Nami loves to punch him. Nami is the one with more chances to become Luffy wife if something like that ever happens.
Franky. Easygoing but not part of the moronic group, he is more of a degenerate than a moron, for that I don't see big links with Luffy. Probably among the 3 with less similarities with Luffy character wise. The other 2 are Jinbe and Robin.
Robin. She is collected, smart, very logical it is a bit the opposite of Luffy who acts on instincts, loud etc. (even if of course Enies lobby shows how truly deep the link is, like for every other crewmember in the end). So as I see it she is the