Note: For trade league it's extremely easy to buy 20%+ Damage over Time Multi for cheap. This is usually a much better option than crafting for an entry level piece.

1. Get yourself a Fractured Marble, Jade, Turquoise, Citrine or Onyx Amulet. You want minimum item level 75 (for the rare chance at +1 Fire Gems — this doesn't scale RF but does scale FT). If you can afford it, purchase an ilvl 84 for a chance at the highest resist roll.
   • Desired Fractures 50+ Life, 10%+ DoT Multi, 20%+ Fire Damage, 30+ Dex, 30%+ Resist
2. Time to purchase some essences! I'd recommend 20+ Screaming Essence of AngerScreaming Essence of AngerGuarantees a fire modifier. Fire resistance on armour, added fire damage on weapons..
3. Spam your essences till you find something with desired stats. 20%+ Multi roll is ideal, but you can also use +1 Fire Gems.
4. Anoint Aggressive Bastion or Unyielding depending on budget.
5. Bench craft:
   • Life
   • Fire & Chaos Resistance
   • Minimum Frenzy