Video Guide
Final Comp
Duelists are insane right now. Not only do you have an insane early game due to the quality of the Duelist units and the power of the trait, but you also cap insanely high due to the power of 8 Duelists and the 5 costs you can include. Those together make this the strongest comp of the patch, to the point where some people are one tricking the comp to extreme success.
Because this comp is more contested than ever, you should be very comfortable with the fast 8/9 version of the comp where you carry Lee Sin/Irelia, rather than the reroll version.
Early Game
Your early game will often revolve around Duelists + Umbral + Heavenly due to the easy synergies between the units. Qiyana or Tristana are great item holders, with your more tanky items like Titans, Bloodthirster, and Steraks going on Darius.
Mid game Board
Add more duelists and win fights because duelists are broken.
Items Tier List
I think this is where most people make mistakes with this comp. Gone are the days of playing for Last Whisper Tristana 3- usually you're playing for fast 8/fast 9 and playing for Irelia carry, which makes slams like Runaans, Gunblade, and Guardbreaker much stronger. Because this is more of a fast 8/9 comp now, you should highly prioritize items for Lee Sin, which is why a lot of his best items are in S tier.