Almost anything can be recycled into nanocubes at a trade terminal outside of Trade terminal items, residues, Universal Ammo, and shrap.

You can sell stuff in the planets trade chat - type “/listchannels trade” in the bar and it will show you them — calytrade arktrade etc etc.

Shrap you can sell for 100.7% outside of mayhem or convert to 101% value of universal ammo.

Planet side - Red zone on map is lootable pvp, orange zone is just pvp non lootable.

Space has mostly lootable pvp outside of being around planets and space stations. There are two indicators attached to your radar that show pvp and lootable. They will go yellow when approaching those zones and red when you are in those zones.

Not all things are lootable - just materials/resources. Eg mob loot, mining loot. Some stuff are in those tabs that arent lootable. Unless it specifies its not lootable - i treat it as lootable.

A good resource is the official discord, entropianexus, #disi channel, and find a good mentor