Just started checking this game out again. Played it briefly quite a few years ago. Sort of getting ramped up again running the military newbie missions. Was wondering: is there anything like an NPC merchant where you can sell lower-value stuff that you loot? Or does everything go through the player market?
Depending on how much you plan on looting, and what skills you may already have trained, there are some third-party tools that can analyze your inventory and current market data to tell you if selling it outright is more profitable than refining it and selling the minerals.
They have made a lot of adjustments to what drops from NPCs, so refining loot isn't nearly as much of a mineral faucet as it used to be (a good thing, even though I do it a lot), but it's still often worth it to refine a lot of the stuff that's less than meta 4 and sell the minerals instead.
As Ichy said though, don't rely on mission running as your sole source of income and entertainment in the game, unless you just really, really love it. There's so much else to do that can make more money or be much more fun, like factional warfare, exploration, etc.
Mission running is still the best (only?) way to raise faction standings though, so they are a necessary evil if you don't have a really good set of great standings already.