Full guide with detailed explanation on everything about Seris mechanics can be found at:
Here's the starter build taken straight from the guide.
Increase the range of Restore Soul by 300% and its duration by 1s.
Your Movement Speed is increased by 40% while any enemy is marked with a Soul Orb stack.
Heal for 280 every 1s while channeling Restore Soul.
Reduce the cast time of Shadow Travel by 30%.
Fade to Black
Reduce the Cooldown of Shadow Travel by 1.6s after activating Restore Soul.
Regenerate 2 Ammo every 1s while channeling Restore Soul.
Gain 21% Movement Speed.
Increase your Mount Speed by 45%.
Reduce the Damage you take from Direct attacks by 21%.
Reduce the Cooldown of all your abilities by 30%.