making credits

if your just starting then your race is terran and thay make there moner from commerical infastructure and research. research commeical and build same on your planets, allso build enough agraculture to feed you population. do the missions and thay will help in understanding the game. allso check out the manuel.

Assuming you are terran, what you need to do is make enough housing to have people to work in every commercial and agri you build
(so have enough to ahve one pop per land on your planet)
then build about an equal amount og agri to make enough food to feed your people
then, build the rest of the planet up with commercial
then reserch commercial infrastructure.
and you will have money`

but that only applies for terrans, other races make money different ways due to their racial modifiers on certain aspects like good production, mineral production, etc etc
to see that go into the manaul and click on "alien races"