Each alien species uses a different resource as their base currency. This makes figuring out a good/bad deal very difficult. This was probably intended to be a fun challenge by the developers, but I found it annoying. In any case, I hope you find this guide helpful.
Guide to Trade Routes
Trade Route Cheat Sheet
Here is a quick reference to what to buy and sell for each aliens you encounter. I made a lot of money/resources early in the game by buying Cobalt-60 from the Ulooquo (since they are encountered early in the game) and then selling it to the Citadel.
- Buy Adamantine and Cobalt-60* from Ulooquo.
- Sell Yttruim to Ulooquo.
- Buy Adamantine, Cobalt-60, Yttrium, Chiralite, Gold, and Titanium from Tycoeden.
- Sell nothing to Tycoeden.
- Buy Cobalt-60, Platinum, Neutronium from Araona.
- Sell Gold* to Araona.
- Buy Adamantine* and Cobalt-60 from Saurid.
- Sell Neutronium* to Saurid.
* = Best deal
Advanced Trade Routes
For those who want a more details of how good or bad a deal is, then this may help. I took the base currency of each alien species and divided by the their value of Titanium, then converted the values of reach resource based on the their price conversion. There was probably an easier mathematical way to do this, but this is what I did.
The interesting fact that I learned from this exercise is that each alien species has a best deal for each buying and selling each resource. For example, the Ulooquo have the best purchase price on Cobalt-60 while the Araona have the best sell price for gold.