It's simple enough
Tier SS
Luffy (Three types of haki, AdCoC, CoC blast, FS, VoAT. Overall the best in all three + he got extras unique to him.)
Tier S
Zoro (Three types of haki, AdCoC, BoAT. Expect him to get AdCoA = blacken his blades but Luffy will get his own version as well)
Tier A
Jinbei (Two types of haki, very experienced user with a high New World proficiency in especially CoA)
Tier B
Sanji (Two types of haki. Has he shown black CoA yet? Way less experienced than Jinbei and hasn't shown any mastery, relying on Raid Suit and DNA at the moment)
Tier C
-
Tier D
-
Tier E
Usopp (unlocked CoO but can't use it proactively. Has access to very good/advanced CoO so he can jump tiers later)
You could perhaps have Luffy down at S at the moment because he has yet to reach the real SS of Shanks, Mihawk and who else is up there but there is a distinction between him and Zoro.