For my first DSLR I actually thought about buying used but there was no K-5 or K-5ii for sale in my region and I didn't want to buy a used one from half around the world. I came accross a K-3 during that time, liked the ergonomic handle, and was a lost case for the used market.
My lenses are a mixture of both:
The 18-55mm kit lens came with the camera as WR solution.
And if lenses I am interested in arn't available used at the time I buy new (Samyang 35mm + 8mm).
And then there are my impulse purchases when I see lenses for cheap and can't resist (quite a few when you check my signature
)