TrackIR is mandatory when you would really be into Sims.
I've got an Track IR 3 as i played LockOn and now for Elite an TrackIR 5.
(Shocked how small it is now.) Still using my old Eurofighter cap
i got from on the 50th Luftwaffe Anniversary Airday for the Tracking Clip.
After i tweaked the curves a bit to get rid of the axis centering it felt great and very natural.
Its the next best thing to Occulus Rift in terms of immersion i think.
You feel so much more as in the Game. And the Benefits for Combat are priceless.
For Elite, i would go for this over a hotas in the beginning, if i had at least a Controller.
I got mine a little cheaper, as it was a Test Model. And don't regret it.
If i had an Webcam, i maybe had tried cheaper solutions first, but since i had non,
i was not willing to spend money on that, only to see me buying an TrackIR later anyway
when i where disappointed by those hobby projects.
If you can afford it somehow, buy it.