First thing you should do is when you lvl up use your skills on economy and not fighting.Put more on energy than enterprenuership so you can earn more gold.
Your first company should be limestone and then switch it with concrete when you get enough limestone.Try to make more companies and dont give people jobs if you dont have a lot of gold.Try to get to 6 companies as fast as you can.
Finish starter,weekly and daily missions and when you're opening cases sell most of the items you get you dont need blue or Better armor at the start.
If you get confused ask your country members for help.