What may seem obvious to experienced growers may be of some benefit to those just starting out . . .
I have found over the years that the utilization of live sphagnum, whether as a component in composts or simply as a top-dressing, offers several benefits to carnivorous plants, one of the chief being a clear benchmark of water quality and, ultimately, that of the eventual health of the plants themselves.
Sphagnum moss is notoriously sensitive to mineral-laden water and will not survive that condition for long. In many parts of the area where I live, for example, the water is so "choked" with minerals that plaques will quickly accumulate in any kettle and coffee maker; so growers generally depend upon reverse osmosis as a source of watering both their carnivorous plants and orchids, since summers in "Kali-fornia" rarely see any rain. The moss also has the additional benefit of providing local humidity for sensitive species and serves as a good indicator of when water is needed, since sphagnum will quickly discolor as it is dries; and it is also highly-sensitive to fertilizers of any sort, indicating through its easily-burned tps, a potential "early alarm" for the grower. In addition, it tends to eventually crowd out any "unwanted" items in a pot. I have never seen Botrytis, for example, where the sphagnum actively grows.
While it may be occasionally difficult to obtain in its live form (though is far more common now), it is a simple task to induce long-fiber sphagnum (either from Chile or New Zealand, easily obtained from better nursuries) to grow from its dried condition. Simply load some saturated moss in a gallon or larger zip-lock bag, allow for moderate light and Tb, and let the innumerable spores do their worst. In a few weeks, you should see some growth.
In the photos below, I simply began with a few large handfuls from a 500 gram bale of New Zealand Sphagnum (Sphagnum cristatum), saturated the mess, and I do mean saturated it, with RO water -- and six weeks or so later:
Healthy sphagnum, more often than not, equals a healthy plant -- and it looks nice. What could be better?