The key to a good trade-driven economy (for any faction, not just TEC) is to build a long trade route.  Early on, you should only build trade ports which expand your trade route.  This gives you the most bang for you buck, and if you set up your logistics right allows you to get by without purchasing any expensive logistics ugprades on your planets.

Be careful when planning your trade route, since adding a new trade port may accidentally make your trade route shorter.  Traders always take the shortest route from point A to point B, so building a trade port that opens up a short-cut could reduce the length of your trade port chain.  Take for example this hypothetical system:

A = B = C = D

||          ||   ||

E = F = G = H

Suppose our trade route is currently B-A-E-F-G-H-D.  Because C does not have a trade port there, it is as if it doesn't exist at all with respect to trade routes.  This gives us a wonderful trade route of 7 jumps.  However, if we place a trade port on C this is no longer viable.  The shortest path between B and D is now a mere two jumps, and the path between them is no longer our longest trade route.  Instead, we get the (much shorter) A-B-C-D-H route which is only 4 jumps. 

I know this is somewhat confusing, trade routes always take a while to figure out.

You actually can't add the trade port to C even after setup up B-A-E-F-G-H-D. The trade port line will recalculate if you do this.

Yeah, essentially you want to avoid creating a loop or shortcut in your chain.  You can curve and weave it through planets, but you always want there to be only one direction for the trade ships to go.  Better yet if you and an ally can make your chains meet and form one gigantic chain(assuming you've signed a trade agreement). 

One thing I'm not too sure about anymore is if trade port chains can still jump through a single uncolonizable zone.  They used to do that, but now, perhaps due to all starbases having trade port upgrades available, the chain doesn't seem to jump through uncolonizable zones.  This actually simplifies things, as you only need to worry about the specific gravity wells with trade ports.

If you use starbases on stars, does it chain through them as well?

Yes the chain can go star to star, but the ships take a long time to jump stars where wormholes are instant. (I'm not sure, not in modding code yet) the trade ports give so much income per sec. so the time the trade ships use jumping stars might be visual only. The A.I. uses the wormhole more and star-bases at stars are vunerable to multiple threats and cannot protect such a large grav well so i use wormholes if possible.

I found that A.I. does not like star-bases at wormholes and will waste fleet after fleet where at a star they just bypass the star-base and go for your planets.