Don't use any kind of dirt or commercial potting soil for your VFT. Most people develop a soil "recipe" they like but the gist is, as mentioned, nutrient-poor soil as in their native environment. Typically sphagnum peat moss and sand is used (1:1 ratio)...you can also add perlite...and some people grow their VFTs in pure long-fiber sphagnum moss. I use a mix of peat/sand/perlite and a little chopped sphagnum.
And pardon me if you already know this, but there is a difference between peat moss and longfibered sphagnum moss. The peat looks like fluffy brown dirt...and the moss looks like dried moss (usually sold in a clear bag).
Just avoid soil/dirt and fertilizer, give it lots of pure water (rain or distilled) and lots of sun and you should be fine.