Will you fight when interdicted or just run?
My trading ship is 8C power plant, D grade thrusters/life support/sensors. 6A FSD. 8A distributor. 4A shield and all the rest filled with 452T cargo bays.
3 fixed large beams, 4 multicannons and huge plasma. 3 A-grade shield boosters.
The jump range is around 24Ly unladen and 17 laden. Good enough for most routes, not max range by any means but you can still destroy any single ship that stops you.