If you want to sell stuff, you need people to buy it from you. People would mostly do that when your ‘trade hub’ is close to their activities, when the trade hub supplies nearly everything they need for those activities and when they can sell their stuff easily (hauling service or buyback). Otherwise they might be tempted to get all the stuff from another market instead.
You mention cores, so I assume you want to do this from within an upwell structure? This has the risk that you need to defend your structure against hostiles.
If it’s just the ‘supply market demand’ experience you want, you could join a corporation in a remote region of space (null perhaps) and supply their market to turn it into a well stocked trade hub. Added benefit is that you have a corporation to defend the structure with you.