List your entry as [W]: <item name> (Job/Level)

Ex: [W]: Mythril Haubergeon (ARM47)

Then inside the post list the materials, put if you have them or if they need to get them, and what you have to offer.

Ex: (recipe copied straight from mooglebox)

Earth Shard (x6)
Ice Shard (x5)
Mythril Rings
Mythril Rings
Mythril Rings
Undyed Woolen Cloth
Steel Plate
Aldgoat Leather

I have the items, and also have #### gil, or other Armorer materials (etc.).