I just jumped in to the DCS world, and am using the Rift. Yes, I actually puked after my first hard bank. Going on day 6, I am still pretty dizzy but I am now able to bank hard and even invert without issue. You just have to power through it. If your body still won't acclimate, definitely get the TrackIR as it is the next best for immersion.
I will say that I will never go back to 2D for flight. Ever.
Best of luck!