There are 2 kinds of Markets in SRCW. One is the domestic economy, which is your internal economy, and the second is the World Market, which as the name suggests, is where global exports and imports take place. All the information for these things can be found under the production tab, and you can also find out how much money you are making/losing each day from a particular product.
Watch the world market prices, and then target that sector if you have the resources to be able to. Due to the way the game's starting economy is, prices will skyrocket for several products on the world market. Take advantage of this to make lots of cash for expanding your nation. You can also raise the domestic prices (but be careful of your DAR) to match these prices, which is often about 10x the production cost of the product, this will allow you to maximize your profit, which can then be reinvested to create and upward spiral of growth in your economy.
factories, etc increase this. Light blue means your factories aren't producing as much as they could, usually because they don't have resources like power, water, etc.
Prices determine this. Raise prices to reduce demand, or lower prices to increase it.
What you have on hand
Make sure you keep your DAR at a level where you have a population growth, because remember, these will help fuel demand in your economy, and cause shortages for other nations (because you are not exporting to them) which can cause prices to rise even further, meaning more money, these extra people also pay taxes to your government, and join your army.
Research can be profitable, if you sell techs to your allies who have money, and this can also be reinvested into more tech research or into expanding your economy.
Tech research can also yield benefits for your domestic economy aswell, such as increasing output of facilities, improving your infrastructure rating as well as giving bonus's to other social programs which means you can spend less to have the same effect, or spend the same to have a greater effect.
Don't rush to build up, make sure you are still making a small surplus at the least, as this can be useful for buying opportune units/techs.
BUILD WITHIN YOUR MEANS
That is the golden rules, don't overextend yourself too much too early, because it will only slow your progress down, which will in turn mean slower development.
There are 2 kinds of nation - a well developed nation and a backward nation - a nation can go into either of these depending on how damaged its economy is after you have taken them over. This means that it may take some time for them to go from being one to being the other by repairing damaged facilities.
This is easier then rebuilding an undeveloped nation, as your GDP will fall much less, meaning people can still buy plenty of stuff from you. This will also mean that they will increase your demand more hten a poor nation.