The number of Poly`s you are using is about correct. You are correct too that mesh smooth (or turbo smooth) is the next step.
But first you need to make sure the whole car is built in Quads, this is the reason the mesh smooth is messing up.
Building a car, and then using mesh smooth is very hard!, and you are doing it correctly.
9 times out of 10, if the mesh smooth is messy, it is because your low poly geo is too messy.
Yout Lambo has so many square edges, it might actually be better to build the whole car by hand, not use a mesh smooth. If you want to keep the straight edges, you might need to add more poly`s along all the egdes.
A good tip is to copy (reference) the car, add a mesh smooth to one, and edit the low poly one in the areas you dont like. Basically you are modelling your low poly version and the version with the mesh smooth changes in real time.
I can say you are correct...but cars are tricky as the mesh needs to be PERFECT for the mesh smooth to work. Make Quads, add more polys to keep square edges etc., maybe adjust the smoothness in the mesh smooth, try turbo smooth also..