@Malintex_Terek:
I'm thinking Lucci has a huge increase in power for his normal Beast-Man form (6000 douriki) while a lesser amount in the Kami Bushin (5000 douriki) but still more than normal. Jyabura and Kaku's Beast-Man forms are not as large as Lucci's (I'm disregarding Kaku since naturally his animal is bigger) so I'm not sure if they would have the same amount of douriki bonus from using them. My guestimate of this bonus would be +1000 douriki for both of them, while +2000 for Lucci (so Kaku's douriki would be 3200 and Jyabs' 3180).
Very interesting estimates. Using your numbers as a base, I'll pull some up guesstimates too: Luffy is about 2500-3000 Douriki at 1st Gear, with 10000+ at 2nd Gear. My only suggestion is that Lucci's bonus from his DF transformation should be much more than +2000, at least doubling that. He was the one who claimed Zoan fruits have little limits to improvement, so I'd guess he had trained his to reach very high figures.
To get any sort of perspective in analysing Luffy's strength, and to find out what Douriki means, I'll have to go with a few things that could be considered off topic…
The only scene permitting cross-Douriki analysis is the moment when Franky got owned by Lucci. I think it's safe to say Franky was about equal with Fukurou, at 800 Douriki, or at least not a relevant distance away. Lucci, at 4000 Douriki, took his strongest attack with a basic Tekkai and then floored him with an unnamed punch. The difference between 800 and 4000 is 5x, so this kind of result should be expected. On top of this we have to consider that taking damage doesn't seem to be Franky's forte. There are several scenes that highlight his low pain treshold compared to for example Luffy, who can take virtually limitless physical abuse from blunt objects.
What about Kaku or Jabura? Could either of them give Lucci a good fight? How about Zoro or Sanji vs Lucci?
A simpler exchange to look into the meaning of a single Douriki would be switching Zoro's and Sanji's opponents, to get Zoro vs Jabura and Sanji vs Kaku. Can anyone claim Zoro would not have the easier time like this, of the two of them? (It's a natural reflection of the type of ranged skills Zoro can employ, while Sanji is still missing his version of Rankyaku.) The difference between Kaku and Jabura is much more than the mere twenty Douriki given through Fukurou's Teawase. I'm basing this supposition entirely on the fact that Sanji is a purely close-ranged fighter and still managed to win against Jabura, meaning the wolf-man wasn't a strategically sound fighter who could employ his Douriki efficiently. I think the Wanze fight gave a good amount of attention to Sanji's problems, namely his lack of ranged skills.
Luffy's fight against Blueno wasn't a traditional fight at all; Luffy was clearly playing around, just using his speed to see how he matches up against a speed specialist. He attempted to reach the ultimate end of his abilities at the first gear, and found out it wasn't enough to create a decisive victory against the likes of Blueno. Worse yet, after Blueno turned to his DF abilities, Luffy's hopes of a quick victory became even more muddled. It was clear that Luffy could finish Blueno off rather easily even without using the second gear, through using his more advanced first gear battle techniques in a fight uncomparable to either Crocodile or Enel -- But that wasn't the type of victory Luffy was aiming for.
However... While I want to claim that Luffy could beat either Kaku or Jabura without resorting to the second or third gears, it doesn't seem plausible examined against the introduction scenes of the CP9 fighting skills and the Strawhat pirates' fighting skill evolving scenes. This is counting the use of DF abilities to the fullest by both Kaku and Jabura. It's also counting the unstated canon claim that speed is the main forte of the CP9, not strength (=Douriki). At best it would become a close fight, good enough for a final fight in any previous arc. Using 2nd Gear it's no competition: I've estimated the difference (10k+ Douriki with 2nd Gear, 3k+ for Kaku and Jabura) at a step or two below the 5x of the Franky-Lucci difference, so I think it's not too weird to expect Luffy to drop either them within about a half a dozen attacks like the JET Pistol and the JET Bazooka, if not less.
If Luffy is that strong with the 2nd Gear, why did the fight with Lucci prolong so much? The answer to this lies in the amount of fatigue this technique generates in Luffy and the superhuman damage absorption of Lucci, which I think was the other reason why we received an otherwise simplistic narrative detail of Franky's best attack being shrugged off by Lucci like it was nothing. Lucci also used speed to his advantage: He jumped backwards to absorb the damage of the JET techniques, while still retaining his ability to charge forward instantly. No matter where he was, when receiving straight hits from Luffy's 2nd Gear he was always hit hard or even blown away, while not getting knocked out of the fight in a decisive way. This is in line with the less-than-1.5x difference in Douriki I assumed between them, if Luffy has something between 10k and 12k Douriki in 2nd Gear. Halfway through the fight Luffy's 2nd Gear lost most of its edge, also making the final parts of the fight uncomparable with the earlier scenes. In the end he overcomes Lucci with pure spirit.
Of course, the conclusions drawn from this pondering include that Zoro using Asura would defeat a gearless Luffy. Sanji with his red-leg kick should be right up there too. To give some perspective to 3rd Gear, I'd assume it was around 30k Douriki, meaning it would send Oimo or Kaashii flying in a one hit KO.