Here is a Reddit post that has lots of resources for Stars Without Number. I highly recommend the sector generator listed in that post. It can save hours of work. Also, don't worry too much about preparing every single NPC your players may encounter beforehand. Pages 190 and 191 of the rulebook have quick NPC stats you can use. Also be aware that at low level, a single gunshot can take out almost any PC, so don't throw anything too deadly at them the first few sessions, unless you like rolling up new characters. If you haven't seen it yet, I also recommend checking out the youtube show Swan Song on itmejp's channel. It is a very enjoyable Stars Without Number campaign, and you can probably get ideas on how to run the game by watching it.
