Only sell the free steel if you need cash.
At one point you will want to expand your buildings and then you need wood stones and steel.
So it is really your choice.
My problem was when I started (one of my many problems

)
Was the lack of almost everything like power and water so don't think you will have a lot of excess power and water, save it, you are gonna need it badly as you get more and bigger buildings.
and the biggest problem : CASH!!
Sometimes I found myself without even enough to pay the 10% marketfee so I struggled many times.
Take it slow and yes look where you put your buildings, plantations green, mines and wells yellow, you can see it when you click the build button.
Just keep selling the raw materials and buy more buildings, more mines, etc.
Fill up most of your slots but not all.
When you have achieved a couple of million of cash, buy a shop,(gasstation or/and textilestore furniturestore) but don't use them yet, start expanding them, little by little, so when the time comes and you are bigger you can start to produce or buy finished products to put in your stores and those stores will have reached an acceptable size to sell with profit.
This is just one strategy of many, I just tell you what my experience is, but others may tell you something different and they also can be right.
But one thing I rhink we all agree on is : produce raw materials and sell as much as you can.
