Considering the current state of things (chapter #1155), I'd rank them as follow (obviously ignoring pirates with unknown status, like Kaido and Big Mom, inactive pirates, like Rayleigh, captured pirates, like DoFlamingo, and non-captains):
- Shanks: I'll put Shanks on the top due to his bounty and bloodline (he still has status, even with severed ties with Mary Geoise, as seen in Marineford). Even without strong allies, we can deduce by the bits and pieces given by Oda that his crew would be able to face any Yonko's fleet or even a stronger force, like the marines... he's just HIM;
- Blackbeard: BB and Luffy are close ones, but I'll put BB ahead due to Aokiji; he's undoubtedly the greatest crewmember (non-captain) of any current pirate crew and hinted to have a decisive role in the final war. Yeah, he's probably only using BB for his own agenda, but so far we can only consider him an asset. I also have hopes that BB's crew will have better showings in the final arcs and maybe Oda will even give him some strong allies (with Hachinosu he possibly might have not only numbers, but some of Ochoku's remnants, for example);
- Luffy: strong crew and allies, unquestionably has the best influence among pirates (from the revos up to key countries like Wano and Elbaf) and is the "choosen one". Ofc I don't need to elaborate much about him... could even go up to 2nd place;
- Buggy: having Mihawk and Croc under him (even if just a facade), plus the Cross Guild's structure, surely make him the 4th most influent. His luck is overlooked, but it might even lead him to the One Piece;
- Marco: from here and on the difference starts to become more evident. Marco is a solid leader, probably can riley up all the WB remnants and most (if not all) the former WB allies and was one of the five strongest pirates during the timeskip (according to the Gorosei), but can't really compare with the Yonko;
- Katakuri: the BM remnants aren't as cohesive as the WB remnants, but he would probably be able to lead most of them. They're still a force to be reckoned with;
- Law: I'll put him below Marco and Kata, just because he hasn't the numbers/influence of the others, despite being a greater threat individually. He also dropped out of the OP's race, according to the narrator, so that puts him under a bad light compared to the ones above him. Kid would be here with Law (actually in a position above, due to having a stronger crew IMO), but his status is still unknown, so I'll leave him out of the list;
- Hancock: I'll put her as an independent party right now, because Luffy didn't really establish an alliance with her, despite being evident that it's practically confirmed (although some people still think that she'll end up joining Cross Guild). Having Rayleigh as an ally is a nice bonus, but as he's inactive, I won't put it in high regard. Amazon Lily is a decent country, but I don't think she has someone that would make that much of a difference if she were to face any of the pirates above;
- Bege: he's on his own now, but probably has some influence in the underworld due to his mafioso style and his time in a Yonko's crew;
- Apoo: has the same bounty of Bege, but probably less influence (although I'm pretty sure that he has his share of influence in the underworld). His crew isn't really that fleshed out like the Fire Tank Pirates too, but he recently probably added some of Kaido's numbers (or at least Inbi) to his band. Either him or Bege would drop out if Kid is alive.