Highlighted weapons are free options.
Diluc has a number of combos he can do during his uptime:
His most common combo is . This fits perfectly into the buff window of his teams.
For high upfront damage, use . This falls off significantly if the enemy is not killed within this window.
A full rotation combo can look similar to . An example video can be found here.
These placements assume strong Flat ATK buffs such as Bennett, as Diluc is commonly played with them present in his party.
Diluc's constellations boost his Skill damage, so talent prioritization can vary from player to player.