Build tall. Focus the planets you do have on production and build out as fast as possible. How many planets do you have? I dedicate at least 1/3rd to research. These planets have at least one factory or 2, 1 or 2 farms and the rest are research buildings. The same goes for economy planets. 

With farms , you dont want to build them all at once. Build the growth building to start with, when they aren't upgrading run birth subsidies, and slowly replace your starting 1-3 factories with farms as you need to expand your pop limit. Then start replacing your tech buildings - slowly. there is a point at which additional farms hurt you - but I think for a decent size planet that's at least 50 pop depending on your tech level