In a purely free-market economy, governments tax and spend, make regulations, and raise armies. That's generally about it. They don't build anything. They don't invent anything. They do not populate new territory.
Every race in Gal Civ is very very similar in that compared to real nations in the real world in real history, they are all on the extreme totalitarian end of the spectrum: communistic...or really, feudal. The Lord of the Manor decides how many of his peasants shall work the fields, and how many shall toil in the shipyards. The lord directs when large masses of peasants shall migrate, and where to. If the lord so commands, every man, woman and child from one planet shall be conscripted into the army one week, and deployed on the battlefront the next.
Oh, Gal Civ races have different model coefficients here and different ship doodads there. But really, every single one of them operates pretty much like the same extreme stereotype of a communist state or feudal manor or ant colony.
Which is fine. Its a game.
But clearly, Frogboy has ambitions to make a more "realistic" simulation with respect to free market economies. This is exciting!
In a society where individuals have free will, and collectively comprise a free market, people and Groups of People consume and produce.
They trade with each other and the governments according to the laws of supply and demand. The government's scrip is worth what the free market says it is. There are rates of exchange and rates of inflation for all currencies, and market prices for all goods and services. Where there are "official" rates and prices, there is also a black market.
There is debt, and there are rates of interest.
There are tax rates. Tax brackets. Tax regulations. etc.
When a government needs to wage a war, technology, production, and regiments can and must be provided by people and Groups of People.
Sometimes, government institutions can direct and conduct technological research. But in a society with a healthy economy, for every Manhattan Project, there is at least one Turbinia.
Twelve men walked on the moon. They got there in ships built by the lowest bidder.
People don't all work for the government. Even the ones that do work for the government generally don't live at the government factory or the government lab or the government farm. Some land is privately held and developed and occupied by homes and businesses large and small. There are civic institutions that, while governmental, are not directly managed by the sovereign.
People don't work for money. They work for (among other things) the things they buy with money. The government factories and farms generally suck at providing such things. That is where private enterprise comes in. Your ability to keep your population happy, to raise sufficient revenue through taxation, to maintain a favorable balance of trade with your competitors, depends heavily on the 50% - 99% of your economy over which you have no direct control.
Unless otherwise coerced, people and Groups of People migrate freely as they so choose, carried in star ships designed, built, and operated by people and Groups of People. Unless otherwise incentivized, they establish their homes, their civic institutions, and their private enterprises on planet surfaces (or in space colonies) as they see fit. If and when a sovereign government arrives on the scene, they can welcome it or resist. They can voluntarily cede space for the sovereign's installations, or they can have such space taken by eminent domain or some other manifestation of threat of violence.
So you are going to set forth the task of simulating all of this and more? In a game that is fun to play? Against an AI that puts up a good fight? Awesome! I can't wait to see how it turns out.
But please don't throw out the baby with the bathwater.
Please make all of the flavors of economic simulation race-specific. Please leave in communist/feudalist/insectoid races with production wheels for the micromanagers.
But...how do you balance a free-will race vs a collectivist race?
Maybe you don't have to?
If a player needs to have a game with perfectly-balanced races, they can choose to include all free-will races or all collectivist races when they launch their game. Only if they draw races of two different types will they have to accept the possibility of a major imbalance.