Early boss kill order for a smooth experience:
Devourer > cold witch > hut witch > rust king
Grab Concentrated Area after killing devourer and Escalating Poison as your 2nd support.
Act 1 support gem priority - Concentrated Area > Escalating Poison > Unleash > Swift Affliction I > Pierce I
To use
Withering Presence in act 1 you'll need 1 piece of gear with + intelligence, it's fine if you don't meet the requirements right away as you'll get more attributes in act 2.
In act 1 it's very important to have gear with flat physical damage to attacks. At lvl 11 you want to get a
Warden Bow, with %phys or flat phys. Use your free storm rune/artificer orb on the bow.
While flat elemental damage isn't ideal, it's still quite good for lvling because
Toxic Growth does do a lot of hit dmg before you acquire all of your poison nodes.
Also look at the vendor in town every 1-2 lvls for flat damage gloves, every flat for the build is massive in act 1
Movement speed on boots is also extremely good if you can find them, try to search the vendor every 1-2 lvls. I would never swap out movement speed boots, only replace them with other boots that have movement speed.
Besides that you're just looking for life/resist on gear, but flat damage is the most important on gloves/rings.
!!!!Important!!!!!
Always salvage weapons with quality for whetstones and always salvage items with sockets for artificers orb, this is extremely important for gear upgrades throughout the campaign.
I also personally prefer to vendor all rares for gold to gamble in act 2 and act 3 for better gear.