At the start of the game you need to get an economy planet asap, take a PQ 11 or above, to help the early game economy problem. Then follow up with the others. Also bare in mind that early game its handy to have two or three generalist planets early on before total specialisation. That helps you get going on all fronts. Specialise as soon as you can as that maximises "bang for your buck".

The simplest way to get going on this is to "specialise" ie dedicate a Planet to either Production, Research or Economy (cash generation), and do it on a rule of thumb of four to one with reference to production. ie 4 production, one economy and one research planet, then start over again and build another six in that proportion - and so on. On each specialist planet, build two at most three factories in order to build the specialist buildings. As to which one to build, take a punt on the tile bonuses, if there are good bonuses for Research, make that a research planet. I usually build one economic building on every planet so I can rapidly upgrade and boost bc production as I go through the techs.

The are as many strategies on this as players, but the specialist route is a good one to start off as its easy to remember and put in practice. You'll evolve your own strategy from that as time moves on.

Key thing to start with is the infamous KISS principle "Keep It Simple Stupid" - its a great maxim - love it

Regards
Zy