Maybe a tech tree guide of the game?

Some researches and technologies have no idea how can be upgraded and i know i am not the only one.
I know maybe it is difficult to make a tech tree , but some hints or some guides it would be very helpful.

I'll assume you're talking about the very common mistake of not noticing that there is a scroll bar at the bottom of the research menu. Scroll over an item and you'll see arrows light up which show pre-requisites and they also say if you need so have a certain building upgraded to a specific level.