Early Game
Find Frostbite
Put Momentum on Frostbite and level it high enough to insta-reset Frostbite
Put Virtue and Metal/Flow on Tranquility. If using Flow, find a source of light damage. Level tranquility 3-5 times.
Other 2 spells can be anything, looking out for Umbral Edge and Arrow Barrage.
Hold onto Guidance, Divine Faith and Clemency if you find them. Use Wealth to make money to afford the full build.
Mid Game
Use Wealth to build a solid bank of gold.
Find Arrow Barrage + Umbral Edge. Having 2 of one of these can work in the interim, but eventually you want 1 of each.
Find legendary essences to bolster stats. Frost + Glacial Core for a ton of DPS + permanent health. Put Protection on Frostbite if possible.
Gather Guidance, Clemency, and Divine Faith. Assemble them onto Umbral and level their quality up as high as possible.
Late Game
Umbral Edge + Divine Faith, Clemency, Guidance.
Arrow Barrage + Glacial Core + Frost.
Every Essence over 1000% quality. Every spell over level 20/30.
Move momentum to Tranquility.