Explosive Shot
Main Skills:

Martial Tempo: Increases attack speed by 25%.
Nimble Reload: Boosts crossbow reload speed by 60%.
Inevitable Critical: Increases critical hit chance by 25% each second, stacking up to 100%.
Ignition: Grants 100% increased chance to ignite.
Explanation:

Explosive Shot detonates your grenades, ensuring enemies close to death are quickly finished off. Martial Tempo and Nimble Reload ensure a fast response, while Inevitable Critical and Ignition enhance your damage and add powerful burn effects.
Herald of Ash
This skill provides a persistent buff that causes overkilled enemies to explode and spread Ignite to Path of exile currency nearby enemies, adding more damage and crowd control, especially in large groups.

Attrition
This is an excellent skill for dealing with bosses and rares. It increases your damage against rare and unique enemies as long as you're near them, stacking up to 53%. It also gives Culling Strike, making it easier to finish off low-health rare enemies.

Passive Tree
The Passive Skill Tree is focused on boosting grenade damage, area effects, attack speed, and overall survivability. Here's a recommended path:

Right Side: Take Remorseless, Feel No Pain, and Ricochet to Path of exile currency for sale enhance your overall damage and ammo efficiency.
Ranger Tree: Pick up Heavy Ammunition for extra damage and movement speed if desired.
Left Side: Go for Battle-Hardened, Mass Hysteria, and Devastation to boost your damage output.
Center Tree: Focus on Grenadier, Cluster Bombs, Instant Reload, and Adrenaline Rush to maximize your grenade and reload efficiency.
Bottom Path: Pick up Repeating Explosives, Giantslayer, and Smoke Inhalation for added damage, and Incendiary for bonus damage against burning enemies.
The tree focuses heavily on grenade damage, AoE scaling, and attack speed for Explosive Shot. Prioritize damage nodes early on, then focus on survivability as you progress through tougher content.