If you think GCII system is overly complicated, check this out
This map is a class 17 planet because it has 17 cities. Each will have a population percentage.
Also you can build space farming sectors (hexagons or squares) outside the radius, but it cannot overlap water and cannot overlap cities. (size should be equal)
Say hello the the city grid, each city has a grid to them, which you designate the houses, businesses and industries. Tools like drag a box or save a city layout will help make this process quick and easy!
(orange) industries is your military production and your social production and cost money to run
(green) houses will determine your max population and you tax them generating income
(light blue) businesses will milk peoples money increasing the cash you gain even further.
(dark blue) research plots, but they will drain the cities income
(gold) plop down a wonder a wonder in any city an wait for it to complete
(purple) choose to build a star port in a city
(red) fortify cities with defenses and set up anti air to weaken enemies air superiority or the planet
everything left over will be given to you in billion credits. As your city evolves you may gain/lose credits depending on the limitations the planet has and which areas have been developed every time you hit the turn button.