Having some dedicated research planets is a good thing, and it's good that you recognize the importance of having farms on your planets. However, you need to have some planets devoted to manufacturing for the purpose of ship building and infrastructure development.
I personally hold roughly to a 1:1:1 principle when it comes to developing planets. This simple ratio refers to how I primarily focus planet development ie for each planet in my empire I generally have 1 devoted primarily to manufacturing; 1 for science; and 1 for wealth. I shake things up a little -- with each manufacturing planet I have contributing to building fleets, I'll add one or two research buildings in among the balance of farms and factories, as well as a diplomatic/influence building in the mix. Each planet should have a specific focus, but there is room for flexibility, esp on the larger/higher grade planets.
This is a really simple guideline, because once you understand the basic meta of the game, there is a pretty good amount of flexibility in how you can approach playing the game, so I don't want to tell you how you should play the game per se.
A few tips I would give as well:
- Use you homeworld as your first manufacturing hub.
- The diplomacy tree is often vital for staving off early game aggression with buffs to your diplomacy modifier.
- Diplomatic/trade relations with neighbouring empires, especially the more aggresive ones like the Drengin/Snathi. Open borders treaty can be something that buys you time with them.
- Ship graveyard anomalies can be a great source of early game, free warships. Don't neglect scooping them up because having warships lessens the chance or impact of the 'ripe for conquest' modifier. If you have the Mercenary expansion pack, the armed survey ships are excellent for collecting these anomalies.
-Think about how you build your worlds regarding adjacency bonuses. Special buildings can helo maximize your planets outputs beyond what they may initially look like on paper. The durantium refinery is very powerful early - mid game for boosting production.
-Try and find the upper limit of population size without sacrificing approval, although I think you already understand this.
-Examine the ideology tree in relation to how you want to play. Each tree can offer huge boosts, especially when times well.