For the purpose of simplicity, I'll only discuss the two kinds of Assassin builds. The Natural Critical Assassin and the Equip Critical Assassin.

The Natural Critical Assassin uses stat points invested into LUK to get Crit. You then use %crit damage gears to increase the damage. These cards would be: The Paper card, Aunoe Card, the 10% Crit Damage 7 Crit Rate cards (Assaulter, Cruiser, Bloody Murderer, Panzer Goblin, Rotar Zairo, Kobold Archer and Dullahan cards). A minor upside of increasing LUK is minor resistance to some status effects.

The Natural Crit build is for new people who have absolutely no money to invest in the game at this point in time. It is inferior to the Equip Crit build that can be made at the time of writing. In the future (or in iRO at least) there's a Natural Crit build that uses Dual Daggers to MVP. That build is the most expensive build but it's the best for boss hunting.

Recommended Natural Crit Stat Range:

• STR 50 to 80
• AGI 60 to 80
• VIT 30 to 50
• LUK 50 to 60
• DEX 1 to 30

The Equip Critical Assassin stacks less LUK in favor of DEX for hit rate and the ability to hit skills more reliably. Dual Dagger also fall under this category in terms of stats. You're going to have to leverage equipment and consumables to raise your critical rate for this build. A cash shop item called Abrasive will make setting up easier. It's part of the reason why I say the Natural Crit build is inferior. This cash shop item gives you 30 CRIT which when you're equipped with Katars means 60% critical rate. You would only need about 15 more CRIT to give 90% critical rate. Another benefit of this build is the availability of using Sonic Blow as a supplement for burst damage in PVP. Not to mention that additional stat points that could be allocated to VIT.

For the case of Dual Dagger Assassins, don't bother with it unless you have access to an Ice Pick or Horse Auger. A Jamadhar[1] slotted with a Sidewinder Card will output comparable, if not superior DPS to your common dagger setups especially if you're fighting a Large monster. Daggers only deal 50% damage towards Large monsters while Katars do 75% to Large monsters. Daggers only deal 100% damage towards Small monsters and it does 75% to Medium monsters. Katars on the other hand do 100% for Medium and 75% for small monsters. Try playing around with stat calculators if you don't believe me. If you're willing to spend cash, the Snake Hat available in the cash shop opens up the Jamadhar[1] slot for an Andre card or for The Paper Card.

This build is for players who have cash to spend whether in game zeny or cash shop items. I wouldn't necessarily recommend it for new players who can't get access to at least a Hybrid Jamadhar.

Recommended Equip Crit Stat Range:

• STR 60 to 90
• AGI 60 to 80
• VIT 40 to 70
• DEX 30 to 60
• LUK 1 to 30

For the skills:

Thief

• Double Attack - 10/10
• Improve Dodge - 10/10
• Envenom - 10/10
• Detoxify - 1/1
• Steal - 8/10 or 10/10
• Hide - 8/10 or 10/10

Switch points between Hide or Steal. I prefer maxing out Steal to help out with quests that require items.

Assassin

• Right Hand Mastery - 5/5
• Left Hand Mastery - 1/5 or 5/5
• Grimtooth - 5/5
• Cloaking - 10/10
• Sonic Blow - 10/10
• Enchant Poison - 4/10 or 8/10

Offhand damage is kind of useless, but there's barely any useful skills in the Assassin tree so you can max it out if you want. Poison React, Venom Splasher, Venom Dust are terrible skills. Poison React is too niche to use, only other Assassins would use poison on you. Venom Dust requires you to spend a Red Gemstone. Venom Splasher needs a ton of setup before it can even be used. Enchant Poison is only semi-useless if you really need an endow and you don't have any elemental weapons with you. Like when you're fighting a Whisper. I'd recommend maxing LHM over getting more levels in Enchant Poison.

Don't take the stat recommendation to heart. Just make sure you adjust the AGI to your preferred weapon ASPD. For example if you're dual wielding daggers, remove all equipment aside from the daggers and slowly tune your AGI to get to the closest whole number for ASPD from stat calculators. For STR, balance it out with DEX and LUK for maximum status ATK gains. For WoE builds, stack more VIT. Sacrifice STR and AGI to get more VIT. Though the priority would be sacrificing STR before AGI.

Don't pick this class if you want to kill people easily in PVP or PVM. It's a horrible class until you get the Assassin Cross power up of Enchant Deadly Poison. Pick this class if you want to be an absolute nuisance in PVP.

For equipment choices, definitely get a Snake Hat if you can. Prioritize lvl 3/4 weapons with higher atk rather than getting lvl 2 weapons with 4 slots.

I'll update this post if you guys give me news on what are new items available. Like Cat Ear Berets, KVM weapons, etc.