The best Mercenary build for the early game in Path of Exile 2 can be pretty broad. Not only is the Mercenary able to apply lots of different ailments and take advantage of various skill synergies, but the game itself has a very wide skill system that lets you specialise in just about anything. Want to use a melee weapon instead of a crossbow? Or even spells? It's more than possible depending on what you choose.
The Mercenary's passive skill tree is set up to accommodate his skills and class playstyle, at least initially, and presumably you chose Mercenary because that appealed to you. Here I'll run through my best starter build for the Mercenary class, explaining powerful early skills to grab and support gems, stat priorities, and passive nodes I recommend getting when you have the chance. Beyond the early game, well, it's ultimately up to you how you specialise and where you go in PoE 2's daunting skill tree.
These are my recommended Mercenary skills to grab early, along with support gems below each that'll really enhance their effectiveness:
This is the first skill you'll get and though a little lacklustre on its own, it's the foundation for one of the strongest early game synergies for the Mercenary. When you freeze enemies with Permafrost Bolts, you can shatter them with Fragmentation Rounds, making them explode and deal extra damage to those around them. If you also equip this skill with the Leverage support gem that buffs crit damage when enemies are immobilized, plus the increased physical damage from Brutality, you have the perfect follow up.
As mentioned above, the early game synergy of freezing enemies with Permafrost Bolts and shattering them with Fragmentation Rounds is really strong, so I'd definitely recommend grabbing this with your first uncut skill gem. If you also add Frost Nexus and Double Barrel you can apply far more freezing and then switch to Fragmentation Rounds to blast enemies apart. If you want to do this efficiently, I'd suggest having two crossbows; one with Permafrost Bolts loaded, and the other with Fragmentation Rounds. This will also allow you to specialize both crossbows in terms of modifiers.
Grenades are one of the best damage abilities for the Mercenary and you'll find them especially useful during bosses, since you can dodge roll, fire grenades, and repeat that process without having to charge up or reload as you would with a crossbow shot. This skill is especially powerful when enhanced with the Scattershot support gem for extra projectiles, and used in tandem with Rapid Fire, since that skill ignites the grenades for extra damage once charged up.
Another useful grenade for bosses and tough single entities, especially when you don't have much time to attack while avoiding damage and need to chip them down. I especially recommend the Corrosion support gem which means you can use the grenade against armour. The Mercenary does have the ability to shatter and consume broken armour with Armour Piercing Rounds and High Velocity Rounds, but that takes up two whole slots. Instead, this grenade can function as a kind of AP AoE early on.
If you want to use your crossbow like an assault rifle, this skill is definitely for you. As this fiery barrage charges up it deals more damage and ignites any grenades you launch so they deal extra damage—which is very strong against bosses. If you enhance it with the Chain support gem, you can deal damage to big groups all at once, igniting them all with a little help from Ignition.
This is one of the first persistent buff skills you'll be offered for Mercenary and it's by far the best in my opinion, making enemies create a small fiery explosion when you overkill them. It's especially good if you're using Permafrost Bolts and Fragmentation Rounds to shatter enemies, since it adds another layer of AoE damage to that, igniting enemies who've also just been hit by icy shrapnel.
Once you progress a little further you can unlock minions in the form of the ballista; either the Tripwire variant, which pins enemies and I'd suggest enhancing with the Lockdown support gem, or the Artillery ballista, which is great for dealing AoE fire damage if you infuse it with the Fire Infusion support gem. This can be handy for igniting Oil Grenades and enemies.
These are the stats I recommend you prioritise initially using your passive board and through gear as well:
Dexterity is the most important stat for the Mercenary since this will let you equip gear with high evasion, and you'll either want that or gear that combines evasion and armour. You'll also want some strength and intelligence in order to equip powerful early abilities like Herald of Ash and strong support gems such as Frost Nexus and Double Barrel.
Evasion is definitely the best defensive stat for the Mercenary, considering the playstyle is about running away from enemies while firing your crossbow rather than facing them down in melee. With that in mind, I'd also recommend movement speed, which you can get by dipping into the Ranger skill tree to the right of the Mercenary tree. Lastly, there's no harm in some armour for if you get swarmed in melee, so you might consider gear combining that and evasion.
As you'd imagine, projectile damage is very good for the Mercenary early on, bolstering your crossbow bolts. But it's also a good idea to focus on buffing your ailments, since it'll enhance your ability to freeze and ignite enemies with ammo types. You can also boost the effectiveness of your grenades by adding some extra AoE to the mix.
I'd also suggest grabbing weapon swap speed where possible, since this will let you hotswap crossbows to quickly combo ammo types and effects.
These are passive skill nodes that I'd suggest grabbing when you can, since they're pretty strong:
It's worth noting that Blur and Heavy Ammunition are part of the Ranger skill tree to the right side of the Mercenary one, but I think it's worth dipping over there to grab these, especially as it gives you early access to increased movement speed, where the Mercenary doesn't have it until later.
Generally, I'd suggest looking for evasion in terms of gear, but if you get a good roll or modifier that adds some additional armour, that'd be worth it, too. Weapon wise, your choice is fairly limited for the first couple of acts, but there are multiple types of crossbow you'll encounter as you progress in more or less this order, and some have inherent traits:
In particular, I recommend the Dyad Crossbow for applying ailments, since it loads an additional shot, and the Bombard Crossbow for grenades as it fires an extra one. Keep an eye out for damage modifiers and consider what you're using each of your crossbows for, since this will help you compliment the skills and ailments you're applying.
