I came up with an idea for an alien race. A race develops in the Magellanic Clouds, and they find a lost Arnorian fleet that was rendered derelict in a battle with the Dread Lords and has drifted, dead in space, all the way to their galaxy. They assimilate this technology and become a superpower in their own galaxy. Then the Precursor ships they found and repaired/utlilized detect the Dread Lords when the Drengin release them. They come to this galaxy to investigate and get involved in the general galactic conflict.

I want their planetary improvements to be weak at the start but at later levels have a networking ability such that, for example, a market might give the planet it is on a 7% economy bonus and then give the entire civilization a 1% economy bonus. The end result is a race that is weak on a small map but nearly unstoppable on a gigantic map, as these 1-3% civ-wide bonuses can add up fast. Their planetary improvements will be costly to offset this effect.

However, my attempts to make this work have failed. It seems like it works only for certain abilities that are not planet-specific, such as creativity. How do I make an improvement that gives a small bonus to the entire civilization and a more significant bonus to the planet it is built upon?