Contract Doflamingo for his network and intel.
Collect all the hax: Miss Golden Week (Colors Trap), Kuma (damage or devil fruit repel), Sugar (Toy Maker), Pudding (Memory Manipulation, switch the memories about who the friends are and who the enemies), Mansherry (healing), Van Der Decken (spy to touch Kaidou and Calamities etc), Caesar (deprive all oxygen in Onigashima, replace it with Shinokuni), Trafalgar Law (soul-switch, Mes), etc. All those can have tactics based on the ability
Make Dofla persuade some Celestial Dragons to ally with even more haxxes with lenient characters like Kuzan, Kizaru, and some generous hax like Fujitora.
ask Shanks for the best sake in the world. Find someone with an ability to make the most lethal poison in the world to mix with that sake. Give that sake as a present for Kaidou. Smuggle those sake to the party and to the water resources of Onigashima (rivers, bathwater and drinking supplies, water torrents, alcohol supplies).
Oh and finally alongside that all maneuver, bring out the raw powers: contact Dragon and Garp and Vivi and Shirahoshi and tell them that Luffy would be killed by Kaidou sp could you please bring the entire Revo Army and that mountain-busting fists and Pluton and all titanic sea kings in the entire ocean to wreak destruction to Kaidou?