Research and factories are only tied to money in that the buildings that provide them almost always cost upkeep. You definitely want to build buildings of both type, though not necessarily on every planet.
One thing you have to be careful of starting out is balancing the maintenance of the buildings you build with the amount of income you can generate. When I first started out I'd often overdo it and cripple my economy because I went overboard with research and industry buildings. One trick I learned that I somehow hadn't thought of previously was to just fill out your planets with economy buildings even if they take up all the spaces after you've built your initial factory (or two) and research building (or two). I also build a morale building at some point fairly early on so I can jack up my tax rate. As more buildings become available to you and your empire spreads out a bit (spreading your tax income as well), you can just build over the economy buildings.
Taxes are tied to population, so spamming economy buildings on new planets only makes sense once you reach a certain pop level. The wiki could probably tell you what that is. It has been so long since I've played I don't remember.
Once things get humming along, I tend to build specialist planets based on what kinds of planetary bonuses I get and the size of the planets. Even smaller planets can be useful as industry-ship builders, small research planets, small economy planets, etc. Big planets specialized a certain way can be absolute monsters, especially if you get some decent bonuses. Having a planet with a few planetary bonuses in industry that also builds the industrial capital and a power plant can help build your military or allow you to build key galactic achievements and trade goods.
That's just some rough info. I'm sure others could improve on what I posted.
On, and this is important when it comes to approval and setting your tax rate.
Approval rating also impacts planetary population growth as follows:
Approval from 1% to 19%: population decreases 10% per turn
Approval from 20% to 40 %: population is static
Approval from 41% to 75 %: population increases according to formula given in the population page (given sufficient food).
Approval from 76% to 99%: 25% bonus growth
Approval 100%: double population growth
You have a global and a planetary approval rating. The global rating affects elections. That is found in the bottom left corner and on the financial management screen. I think your global approval needs to be 44% (IIRC) to win an election. The planetary approval affects population growth, and the planetary approval will be based on pop size and any morale bonuses you are getting (global or from specific buildings on the planet). In the beginning, your capital may be at 44% approval because of the population size, whereas the first planet you colonize will be close to 100% because it is so small. It can be nice to get double population growth due to 100% approval on newly colonized planets in the beginning if it means moving the tax slider only slightly lower.
Controlling approval, morale, taxes, and maintenance is part of the fun balancing act of the game.