I mean rallying was a poor choice for getting used to it lol… the only thing worse driving wise would have been go-karts!
Try something tarmac based, ideally with VR options that allow you to lock to horizon to varying degrees (like AMS2, PC2 etc). Some have a preference for either way, to me personally I find a good % of horizon lock is the most natural feeling as it mimics how your head/eyes compensate for motion in reality.
And the big key - don’t try to push through. Sickness starts, stop immediately and have a break.