Weapons are the main focus about the duelist. Some weapon abilities just do more damage other's are special like the dagger where it teleports you or staff that increases evasion.
For subclasses you have champion where she can now use 2 weapons and monk that has special abilities like gladiator.
Champion let's you use two weapons using twin upgrades talent if a weapon of higher or same tier has more upgrades the lower upgraded weapons will now have the same amount of upgrades.
Monk is like gladiator she has special abilities after killing a enemy she gains one point. If you have a tier 3 or lower piece of equipment you can use the unencumbered spirit talent to increase the amount of points you get for killing enemies.
For crown abilities chose the one you want. Challenge freezes time so it's just you and the enemy you choose to fight. Elemental strike will shoot a different type of effect depending on your weapons enchantment Feint I'm not sure how to explain but you move to a tile leaving the enemy confused.
My suggestion is to get decent armor to use like a +6 plate works and the rest to a weapon but that's just me.
Well I'm not sure if this is what you are looking for so hope this helps in a way. You should check out running from cake he makes videos about the game you can find a much better explanation about duelist.