Conquering a colony will increase your income by 2 to 8 metal a tick. Conquering a few colonies will help increase it by quit a lot.
Raising outposts also give you 300 metal, 200 oil and gives you 5 workers
So capture outposts and then raze a few.
Having a larger worker population increases your income. Conquered colonies will give you +1 worker per colony conquered every tick your worker growth comes around.
Capturing wreckage's is also an easy way to gain resources. These will give you either metal, oil, workers, energy or blue tokens. Keep an eye out for these and grab as many as you can
You can also play the mini-games to receive a small amount of resources in game. While they don't seem much, if you play them frequently the amount of resources you can collect from them is fairly high for the early game, which allows you to build 1-2 more structures that you wouldn't normally be able to afford
Lastly, there are many ways to acquire blue tokens. If you hit boost and then free tokens, all the options are available there. While surveys don't give you blue tokens all the time, I've been able to get 500 blue tokens at the start of an era doing these.