do you have economic starbases

Are you using economic starbases and the political government bonuses? And then, have you touched the planetary wheel? It should be easy to get enough income that way if you specialize properly. Also, don't bother trying keeping up with AI fleets, quality over quantity is the way to go. 

You need more research planets. Almost every planet you can afford to have doing research should be doing it. Also, food is a thing here. You don't want just a pure research improvement planet, get some food improvements and grow some population when you can. (just don't go too nuts with it at the start, growth is kinda slow)

The top part of the bottom tech tree. You get 10% first tier, then 20% and 30% next in the second tech age. These are raw production modifiers, so they boost everything. And about economic starbases, one economic ring boosts raw production by 10%, so try getting 4 starbases up around your most important planets asap. The modules themselves aren't that important, just get the rings up. You can get even more rings with the increased range tech from sensor support, but that is kinda late game. 

Production planets should have some money improvements on them, so you can switch into more money if needed. (I prefer smallish planets for this usually) But the "main" planet should be full on production focus only, that's where you'll build the big ships. There is no fixed ratio. It all depends on planet quality etc. Once you get a really good money planet going racking in 500+ per turn, you should be fine, and you could even switch to more production on the smaller planets. 

I use a 1/3rd of colonies for each grouping.  1/3rd wealth planets, 1/3rd research and 1/3rd for production.  Wealth planets should be just that.  And don't forget to increase population.  This version places much more importance on planetary population.