Do you build any specialized economy colonies?

I totally apologize.  I just noticed that you posted this under Gal Civ III.  My response is for Gal Civ IV.  Haven't played Gal Civ III for a long time.

Yes, I absolutely do.  I can usually get at least 1 planet up over 300.  Here are some of the things I do (in no particular order) to boost planet income.

1. Find a planet with high base income and at least 28 tiles to be you Income generating core world. (in this case I took over a planet thru cultural domination that was better than anything I had).
2. Use a Governor with the Income bonus if you can find one, but a Governor 
3. Colonies a bunch of feeder planets to send income to core income planet.  Make sure you pick Orbital Market as one of the Orbital upgrades on each colony.   
4. Build as many Financial districts as you want (Toria has 13, but I could do more). 
5. Build a couple of Housing districts to boost pop and and make a bunch of citizens with high Social Skill Entrepreneurs (I have 7 out of 13)
6. Research "Genetic Architecture" to boost all citizens Social Skills by 3
7. Unlock Ideology "Self-Reliance" under Individualism.  This will also boost Social Skill by 3.
8. Surround your planet with Economic Star bases -adds 5% each (I usually do up to 4, but only have 2 around Toria currently).
9. Add Trade Station modules to each Economic Starbase.  
10. Build a "Governors Manor" on a tile that boosts the Gross income bonus to at least a level 4 (that gets another 20%)
11. Build Mining Bases on any nearby asteroids for another income boost.   
12. Check out the screen shots below for any other hints I may have missed.

 I don't think if there is such  a planet quality in vanilla GCIIII.

 I am playing vanilla so no governor for me.

 There is no such a thing as feeder in vanilla GCIII to the best of my knowledge.

 The best economical colony improvement I can build is shopping center which is tire II building.

 I am not aware of such an improvement.

 I am afraid that I am playing GCIII

 I was planning to do that. But my planet make 65 credit apart from tourism which is 150. So building star base does not give enough boost given the fact that my tax rate is 25%.

 OK.

 Hmmm, I am not sure if I have access to that in GCIII.

 I didn't know that would help.

 Thanks for the screenshot.

mokus5679 - see post below for Gal Civ III info.

Found an old Gal Civ III Crusade save in my Dropbox folder.  I'm on turn 92 and my Civ Capital is producing 129 gross income (119 net). Here are a couple of screenshots.  Also, Starbases in Gal Civ III give a 30% bonus with the Promenade module, so they're definitely worth building. 

Note: I'm not really trying to make this my wealth center. I don't even have any citizens assigned to Wealth yet.  I tend to concentrate on Science.

 Thank you very much for your response plus screenshots. I found out that Terain are not a good race for economy since their best economic improvement is shopping center which is only tire II. I found out that Iridium are excel in economy so I consider them later if I want to get the advantage of economy.

Glad to be of some help   

Spoiler Alert - Just remember - Money can't buy happiness   

 Thank you very much for your reply. I also recognize that my economic planet somehow makes much less tourism income so apparently it makes much more money than I first thought around 150 credits.