All trades end at Hotan, you get the speciality goods as random drops from killing mobs or from looting Consignment trades (Enormous Npc trades).
--> not sure if that server is still alive but i got a decent guide from it
A simplified guide from Myth Online
Introduction
Select a job and visit a job npc to get started.
Job selection can be made from the Character Select screen.
All towns have 'Trader'(Hunter) and 'Smuggler'(Thief) npc.
These npc deal with most of your job activities.
Job Quests
Complete quests to increase your job level.
It's recommended you do not start with high level quests, because your transport has low health.
Collect trade goods and return them to the npc.
Use the Merchant Pipe skill to summon a quest transport.
Target Trading
Target Trading requires Specialty Goods Boxes and the Trader Pouch skill.
Monsters drop Specialty Goods Boxes. Fill your pouch and visit a job npc to get started.
Start in Jangan or Constantinople and travel to Hotan to complete the delivery.
Use the Caravan Bugle skill to summon a trading transport.
A successful delivery will be rewarded with Stones.
Consignment Trading
*Please like the video if it helped. Full credit goes to scatchntrance.