Depends on what you're using it for. If for quality film raise it until it looks convincing. Use the smooth option with subdivision in iClone and try animations at different settings. Usually cloth needs hi-poly so I'd imagine in order to get your hair flowing silky it should be (up to 20k) as recommended for cloth but because it's long hair you might need extra. iClone will give you a warning if you go too high but that  to happens if the original mesh is higher than 20k. 

Thanks for your specs!



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