You are asking the right question, economy is usually what decides who wins.
First lesson: scout and react
Find out as fast as possible (in the first minute) if your enemy will attack you soon. Because you don't want your economy to be killed by his raiders. You should always be ready to defend with your own units and commander.
hint: build radar to spot incoming attacks
protip: try to attack him a bit to distract him from attacking you. 2 reasons "Offense is the best defense" -Napoleon and "Don't try to make your econ grow faster than his, try to make his grow slower than yours." - KDR_11k
Second lesson: you can never have enough mexes
Early in the game, before or after making your first raiders, make a constructor to expand in another direction than your com. Take a mex cluster, then put down solars (or wind on high maps), then continue taking mexes.
Make a constructor for each 3-5 combat units you make, send them to expand in different directions, let the second one build energy and later caretakers and fusions, use some for reclaiming,repair and setting up defense.
hint: use areamex "W", to quickly order a con to take mexes in an area.
Third lesson: Priorities
These are essential for early game economy, and continue to make a big difference in the late game.
You can set which build project gets resources first, so they finish faster than the others.
In general: prioritize what you need: build a caretaker when you don't have enough buildpower to spent your metal, prioritize solars when stalling energy, prioritize emergency defense towers...
You always need more metal, so put them on high prio as well*.
hints: always give your com high prio, so he can quickly make defense when an attack coms, make solars when you stall energy,...
* in the menu there is a setting called "initial unit state", which you can/should set to be high priority for mexes
Fourth lesson: reclaim
Another reason to have constructors near the front: reclaim the wrecks of your fallen enemies/units! It's basically free metal! And you don't want your enemy to have it!
hint: when there are a lot of wrecks (500m or more) around and you have time to reclaim them, build a caretaker (or more) to eat it faster!
to be continued...
