ROTATION:
The core rotation for damage at the beginning is 
Whirling Slash > Whirling Slash > Whirling Slash > 
Twister. Once available, 
Ice-Tipped Arrows and 
Barrage can be inserted at the front of the rotation as they become usable towards the end of Act One.
While purely optional, on longer fights (boss fights especially), it's optimal to use 
Parry > 
Fangs of Frost to force elemental ground for a long duration. This imbues subsequent Twister attacks with more added elemental damage. Several Twister rotations can fit inside this window of opportunity.
SPIRIT GEMS:
War Banner is the first spirit gem to use. While mostly available on bosses only, this provides a huge damage boost that shouldn't be taken for granted.
GEM LEVELING:
Whirling Slash should NOT be leveled up. It remains at level one to reduce the mana cost of the skill as much as possible. This is especially important in the later stages of the game. All remaining skills can be leveled to their maximum capacity, pending attribute requirements.
WEAPON SET ASSIGNING:
To assign a skill to a specific weapon set, open the skill window and click the checkbox for the desired weapon set (both are checked by default).
In preparation for allocating weapon set passive points, 
Whirling Slashand Fangs of Frost should be designated to weapon set one, while Twister is designated to weapon set two. All other gems can remain assigned to both.
While not part of the formal guide, 
Pounce is great for getting around early in the campaign, and 
Shred can be used as a no-cooldown trigger just for entering Werewolf form in a separate weapon set. Once weapon set points begin being used, and especially once 
Dance with Death is allocated, the advantage of a Talisman weapon swap disappears.
More on how to assign weapons and passives to their preferred weapon set can be found in their respective sections of the guide.
Mercenary
Gemling Legionnaire
Advanced Thaumaturgy.
