Gear
Tier Sets
Once you acquire your 4-set, your gameplay is going to change a bit since you get a free Starsurge of Starfall every time you enter an eclipse. It is important that you make sure to spend it before over-capping your astral power.
Trinkets
Raiding: Whispering Incarnate Icon and Furious Ragefeather will be the best options for raiding.
Mythic+: Furious Ragefeather and Eye of Skovald will be best for Mythic+. Whispering Incarnate Icon can also be used here if you don't have one of the other two trinkets.
Crafted Gear
You want to craft an Elemental Lariat at 418 Item level as a priority, followed by your weapons (when you can). A ring is the best option after that.