The basic idea of the system is simple, you buy goods at one location, then move to another location and sell it for profit (sometimes you might lose ducats though). However, there is more to it than that because along the way you might be attacked by bandits and how many goods you hold will be limited by what type of transportation you choose as well.
You will be given 300 Ducat to Start Out (Use it wisely... Player cannot trade Ducats with each other.)
First thing to note is that there will always be 3 Fomor NPCs at the trade post, an Orge, a Goblin, and an Imp.
Orge: 90% repair rate, handle transportation service (Horse, Elephant etc.)
Goblin: 95% repair rate, handle main trade interfaces
Imp: 98% repair rate, sells fomor weapons, Falias Artifacts, etc
Let's take a look at the trade window interface:
The left side are the goods in the Commerce Trade Post, these items cannot be equipped or used by you, they are solely for trades. Each of the items have 2 values, how much it cost in Ducat and the weight of the item. In the example image, the Incubus Suit has a value of 5150 Ducat and 22 Weight, these values will determine how many you can purchase and how much you can carry.
The Middle window at top shows how it sells at a different city/town, the blue arrow indicate that loss of profit, the red arrow indicate gain of profit. In the example if there's gain of profit for 2 and 3 Ducat at 2 different towns, so if you were to sell 1 glove you would gain 2 or 3 Ducat from it depending on which town you choose to go to. At the very bottom there's the trade button to purchase/trade the item you selected. At the bottom it shows you the maximum amount of the item can be stacked and the costs.
The the right side is your loads/goods you are holding. At the top you can choose various of transportation methods, in the image it is the wheelie cart. Next it shows you the weight load you are able to carry, which is 800. In the example of Incubus Suit, you would be able to carry 36 Incubus Suit if you had that much Ducat (Remember you have to purchase then sell, so 36 suit is 185400 Ducat). However, that is not all, because different item have different stack value and different transportation method have different space. For example, if the Incubus Suit can be stack up to 5 in one space, and you have chosen the travel by foot, you can only carry up to 20 Suits assuming if you have sufficient funds, because that's how much space the method has. Below is a list of the cost of using particular transport, and the space/weight for different transportation methods:
Baggage by Foot (400 Weight) Cost 0 Ducat, Human running speed, 4 spaces
Wheelie Cart by Foot (800 Weight) Cost 3000 Ducat, Giant Running speed, 6 spaces
Horse Carriage (900 Weight) Cost 100k Ducat, Shire Running Speed, 8 spaces
Elephant (1700 Weight) Cost 350k Ducat, Elf Running Speed, 7 spaces
After you have decided what to buy to trade, then you are set to make your away to the other trade post to sell your goods and earn the Ducat.
Once the commerce starts, your damage will be reduced by 40~50%. You will not be able to use another transportation methods like pets, goddess wings etc... until you have complete the trade. You cannot enter housing channel either, please be aware of that.
On your way you might face robbers robbing your goods, defeat them and you can get robber scalp dropped by them or special robber clothing. The robber scalp can be sold for 10, 100, or 1000 Ducats depend on the quality of the scalp (ranked from bronze, silver, to gold).
The higher rank the robbers, the better scalp they drop. The robber's strength is based on the goods your are carrying and the distance of the travel. When they appear, the robbers will spawn in groups of 1~8, if is 5+, there will also be a boss robber(kingpin) along with them.
When the robber try to steal your goods and succeeds, they will have a star on their head, after 5 stars, they will run away and you will lose a fraction of your trade goods.
One thing to make sure is that you can choose to avoid bandits or engage them in combat. However, once you engage, you must defeat them all before you can move on.
After you have made to the other trade post and trade the goods, you will gain Exp, Ducat, and Credit points.
Credit points is used to level up your credit level at various Commerce Trade Post, where with higher level, you will be able to purchase better trade goods to trade to the other trade posts. The current max level is at 9.
In addition, higher level of the Credit level will allow you to purchase the Trade Goods at a discount rate:
Level 5~6: 1% off trade goods.
Level 7~8: 2% off trade goods.
Level 9: 3% off trade goods.
You may cancel the trade convoy at anytime without completing, however you will lose a percentage of you total ducats in trade. This also applies if you were somehow disconnected from the server while in trade.