The build defining item Flame Whip is accessed using Flame that are created by Anvil. You can consider postpone the crafting timing if you don't have reliable spike generation (Pineapple, Djinn Lamp).
Note on Utility Pouch: This bag is preferred over the Duffle Bag for its passive +30% damage and a better rage timing. Since it also give -30% trigger speed, flat speed item is needed (Fanny Bag, yellow gem, Gloves of Haste, etc.)
Oil Lamp: Need 1, and buy it as top priority. Helpful from the early game to lategame.
Djinn Lamp: Generate spike for your Flame Whip and give it a big damage boost. Ideally need 2. Will need blue gem in your armor slot to generate the needed armor for its activation.
Wolpertinger: Mandatory for any heat stacking build. Need 1 for this build.
Box of Riches and Glowing Crown: We need small gemstone and constantly combine them to generate Flame, and also to activate Anvil since these are 1x1 item. Need 2 gem boxes. Need 1 or 2 Crowns (2 are ideal) to make King Crown later that has empowered gem slots.
Gem priority: Yellow and red for armor slot. Yellow can provide much needed attack speed in early round but in later rounds should be used to provide stun resist and crit resist. Red increase healing and counter enemy healing reduction. Purple can be left in backpack for debuff cleansing, we have too much scaling as a heat stacking build and should not be worry about enemy healing, can be activator for Anvil this way. Blue: need a total of 7 armor per 5 mana for Djinn Lamp activation, which can be 1 flawed in crown and 1 flawed in normal armor slot. Green and Burning Coal: activators for Anvil.
Paradise Birb: Greatly increase scaling for any heat stacking build and counter Cap of Discomfort. Almost mandatory. Take extra caution on position. This item's effectiveness depend on how good is your positioning.
Moon Armor: Good debuff counter and generate mana. Give very nice frontload armor. Gem holder.
Mana Orb: Even more mana is never a bad thing.
Shelly and Turbo-Shelly: Value-dense 2-slot item. The cleanse amplification is very helpful against the Corrupted Armor matchup.
Stone Helm: Another 2-slot item that is a gem holder with 40% stun resist. 1 or 2 is needed if yellow gem doesn't show up.
Prismatic Orb: 1 is needed for the bird. Additional orbs is welcome, but should be bought on sale or when money is abundant (last round for example) or when other core items are obtained. Take caution on positioning to touch as many holy items as possible to give bonus healing.
Note on the Smithing For Dummies skill: this further reducing weapon stamina cost to a maximum of -65% with Anvil. This allow for 1 more weapon to be used with the Flame Whip. The prime candidate is the Burning Blade, which can be crafted using Flame.