you can make a run out of anything, how bout water? EH?! everyone loves water, seriously. 15 credits on some random planet and sell it at a base of some sort, usualy in omega, even if you dont want to go to pirate bases, you can take it to solarius or something, turns 70k into over a mil or something, i dont remember.
or interhouse trading, optronics from leeds to cambridge, about 5mil investment, 7mil on cambridge, easy 2mil!
another, planet harris, 799 per prisoner, take them practicaly anywhere and you've got a profit, even back to leeds its about twice the price, whatever you invest you double up on.
Also, after reading the new ID proposals you'll notice that trader ID and zoner ID are now limited in cargo space, so you've pretty much got to join some sort of faction to keep that adv. train, so find some kind of trade RP, if you're synth food, trade lux food from cambridge to somewhere in liberty, even to curacau its a chunky profit, not power trader level, but why does it matter?
miner? trade minerals from falkland or something, the source will give rock bottom prices regardless of if they're super profitable to some OORP location, Niboium from falkland to say, Kensington if you're a IMG trader is perfect RP (IMG > gateway base), and its reasonably profitable.
just remember what the factions RP is, and search for where their goods sell well. haulage corps can do most things and can operate from the trading platforms such as Kennsington and uh, whatever the other houses use.