“Consider the simple act of trade. If you believe that possession of an item would increase your happiness, and if my happiness would be increased by selling that item to you for a certain sum, then the trade makes us both happy, and the amount of happiness in the universe is increased.”
- - Tablet of Prosperity No. 4
In the Civilization stage, an economic nation can propose a Trade Route with another nation. If that nation's relationship is above 15, the Trade Route will begin, and depending on the amount of Eco . After a Trade Route is proposed, a road forms between the two nations. If there is an epic standing in the middle, it is harder to trade as you have to kill it, charm it out of the way, or guide the vehicles around it. You can cripple a Trade Route`s profit by destroying economic vehicles that are aiding your enemy. They are also a viable source of money, as when goods are "delivered" by your vehicles, they give about 150 Sporebucks. It can be somewhat profitable overtime to have a few economic cities and establish trade routes with allies.
If you are an economic nation and the only nation left on the planet other than yourself does not have a +15 relationship, usually you can trade with them anyway as long as they do not hate you.
In the Space stage, your empire can propose a Trade Route with any empire that has at least a +30 relationship. A Trade Route will then be enacted, and the Economic takeover bar will gradually fill up. The world your planet is trading with will give spice to your planet, so if you visit your planet, it will give you two spices, unless it is the same type on both worlds. Once it's full, you can purchase the star system for a reasonable amount of Sporebucks, which is based on how many planets are colonized and their T-scores. However, you can only have a limited number of trade routes at one time, so it's a good idea to spread them out amongst your friends and allies. If you have filled up your trade route bar, you may purchase the system.
However, if the empire demands more money for purchase, you will have to start over the trade route activity. Or, you can contact the empire, open up diplomacy, and select the option " End trade route", and you will not trade any longer, you may wish to continue the Trade Route to have a profit in Sporebucks than buying the system, this is a strategy when requiring more cash to:Buy another Solar System that doesn't require too many Sporebucks, making better colonies (both in defences and spice profits) and to buy ship gear or any other gear (Colony Incredipacks, Stellar Drives, etc.).
Your relationship must be at least +50 in order to establish trade with the Grox.