You have many options here. "Best" is a relative term.
My preferred options are bark mix and sphagnum moss. Bark mix is readily available and good for heavy handed waterer like myself. Sphagnum moss holds a lot of moisture and needs less frequent watering. I find bark to be more forgiving, but sphag may work well for you.
Mmm, Yes, I seem to have had the best results with just a medium or medium/coarse fir bark (depending on the size of the plant). Anything that has been in s/moss or 'heavier' types of mix tend to stay too wet for me as my conditions aren't suited to them. As a result, I water every week or every couple of weeks depending on the season, but that's ok for me as I grow Lilies as well which have the same kind of schedule.