If it doesn't have many roots, it might be best to use some sphagnum moss as the medium. And then when the roots develop some decent size, switch to a bark medium.
I know from first hand experience that moss can be a tricky medium to work with. It's very easy to over-water and run into root rot. Orchid retailers use moss for convenience (less watering needed), but after the blooming cycle is over it is best to repot with bark mix. I wish I'd realized this when I first got started, as I think I'm going to have more root rot to contend with after this cycle. But I'm definitely moving onto bark as soon as it's appropriate.