Rebel Galaxy Outlaw.
I've spent most of my time doing side stuff. Board and guild missions, trade runs, the occasional story mission.
Then I tried out mining. Holy jeez, if you want to make money fast go mining. It's so much more profitable than running missions. Many times more profitable. I spent a few hours mining in Texas (the starting system), and ended up with a fully equipped Coyote (the best combat ship I've found in the half of the map I've been to).
My advice is before you go mining give it a think first. How important to you is the sense of progression through upgrading your ship and equipment? If it's not important: go mining. If it is: maybe don't.