It depends strongly on your desired configuration, but if you want to engineer for max. range, then here is the list:
Absolutely necessary:
1) Felicity Farseer (for FSD, thrusters G3, and PP G1)
Very useful to know:
2) Bill Turner (life support G3 and sensors)
3) The Dweller (power distributor)
Won't be superfluous:
4) Ram Tah (heatsink)
5) prof. Palin (thrusters G5)
6) Hera Tani (PP G5)
7) Selene Jean (armor)
8) Lori Jameson (life support G4)
9) Tod McQuinn (railguns) -- with plasma slug effect you might use one as a fuel vent.
UPD. And yes, there is also 10) Lei Cheung (shield generator), but since we are talking about DBX with only 6 slots -- there are a lot of much more useful things than shields
And if you still didn't bother getting FSD booster -- time to think about it
Well over 70, actually
And, by the way, she is still comfortable to fly, except for slow scooping speed, but that's an inborn "feature":
https://s.orbis.zone/sdq