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Personal trading via capship
I'd prefer to leve this until v4 becomes live, but ATM (other than the standard buy low, sell high - & get your trades in first) smalltalking multiple NPCs to gain stackable discounts can work effectively. if a little tedious..
Personal trading via Skunk
As above, but there may be a few traders on the station that have different prices for their wares; worth checking if you want to buy a bunch of green marines or sell off your illegal wares from a distance!