Just to clarify the enhanced thrusters:-
At Felicity's outfitting (and Elvira's), you can purchase enhanced thrusters up to module size 3 - that is, Adder, Hauler, Courier, Eagles, Sidewinder. These give a significant increase in speed and manoeuvrability.
The A3 thruster are upwards of 5 MCr, so it's not a cheap upgrade!
Once you have one, you can have your engineer modify it just like any other drive module.
The drawback is that the power draw is increased, as well as heat generation. On the Courier, you'll need to reduce the weapons and shield until you can get the enhanced power unit modification - the heat generation is something you have to manage..
For budget ships, the T6 with A thrusters, FSD and fuel scoop will do the Sothis runs without too many problems, Vulture for combat.
Upgrade to the Clipper for best trading and moderate combat (good weapons use gimballed, weak shields, but can run fast!). It's much cheaper than the Python.
For higher level combat, FAS or FdL, but you'll be reaching trader tycoon to have enough Credits for those.