Gems are a must for evolving in Archlight, each helmet, armor, legs, boots and weapon can have up to 8 slots for gems.
Those slots can be opened by using Regrade Keys. Gems are made by Jewelcrafting and each gem have 2 possible effects.
When you log into the game your armor & weapons are read in this order,
1.) Head
2.) Armor
3.) Right (trinket side weapon)
4.) Left
5.) Legs
6.) Feet
So to achieve the best results against diminishing returns place your Gem's "Highest rolls" onto
your items in this order.
-from first to last