To make it somehow simple, i watched a youtube video (cant be to look it up, takes longer than describing) just before the release.
The guy there gave me a hint which actually makes the game straight forward and easy if you need some credits at the early (well probably later too) stage:
Dock on a station, go to the commodity market, there you will have several columns. The far right one tells you the average price of the goods in the universe.
So, now, you look for an item in this list that has a very very low "Sell" price compared to the "Average price". You load up your cargo bay with it, travel to the next star system in the hope that the station there will buy it for double the price you bought it for. Easy.
I did that yesterday with the H.E. suits. Average price in the universe was 250, i bought it at the station for 100, and sold it only one jump away for 270. I did that a couple of times and i had some credits to start with.
Good luck.^^