Hi,
I planted mine in regular garden soil(good ole topsoil) And in a very shady spot. I likes the shade. It has done very well.
Alex

Regular old, well-draining garden soil will be fine. If on the very acidic side, you could amend with a bit of ground limestone, but I find my hellebores tolerate my slightly acidic soil just fine and thrive. And I wouldn't site in too much shade. Hellebores are not the heavy shade lovers we are sometimes led to believe and they will be more upright in habit and flower more heavily if provided at least part sun conditions. I have a number of species and hybrids growing in full sun and they do very well.