We need to improve the planet and built tradeport tooltips. However, if you hover the tradeport structure in the area where you would build one, it shows you what that planet provides in terms of trade. The rough gist of it is some planets can handle more imports (e.g. Terran planet -> large population, more demand capacity) and some are better at exporting (e.g. a Volcanic planet can export tons of metal). The addition of TradePorts will amplify import/export capabilities of that particular planet. The improvement to each property is shown when you hover over the tradeport in the build menu.

Here is the tooltip for the tradeport on a Terran Planet:

You can see that if you build 1 tradeport you get 1 import and 1 commercial (credits) export.

If you build 4 tradeports you get 3 imports, and the ability to export 3 commercial, 1 metal, and 1 crystal.

More details are here: https://forums.sinsofasolarempire2.com/517331/page/1/#3881531:~:text=More%20to%20come!-,Trade%20Revamp%3A,-Changed%20how%20tradeports

I too am still insure how the new trade system is supposed to work overall.

So in sins 1 you build a trade station connecting every planet in a big chain and get more credits.

If i understand  correctly, the new trade system in sins 2 is completely different. 

you are not supposed to build 1 trade station at every planet right?

Because when I do,  i do not see any benefit, i see trade ships traveling everywhere, but as far as I can tell you really don't get anything by doing that.

it seems that now in sins 2 you should focus having multiple trade stations on specific planets, like 3 trade stations on a Terran planet to import, and a few stations on a volcanic or ice planet to export. 

To be clear, Trade stations no longer need to be chained connecting every planet together right? That's now how it works now?

just focus on a few specific  planets having multiple trade stations?

I gotta have more credits, I have a fever, and the only cure is more credits.

I'm having fits trying to get a strong enough economy to compete with the ai on nightmare and impossible.

(I'm sure the ai still cheats its economy, which is completely understandable)