Definitely the Greensmix® Sphagnum Peat Moss - that's the good stuff for your fly traps
Don't get the peat humus.
Any sterile perlite will do for your 50/50 mix (you can assume perlite is sterile if the bag just says that it's plain old "perlite").
What I do is get a cereal bowl, a huge bowl, and a large jug of distilled water.
Scoop an equal amount of perlite and sphagnum peat into the large bowl.
Mix the crap out of it.
Add distilled water. Mix some more. Keep adding water until the sphagnum is dark dark brown to black, thoroughly saturated (but not oozing / watery) and work out the dry peat clumps so everything gets wet.
Chuck it in the pot (fill to the rim, it'll sink a bit on its own), make a hole with your finger, pot your VFT, rhizome just below the soil, or right on the soil line.
Cover up gently. The less you disturb the roots the better.
Put the pot in a 1" tray and add water until the tray is full. When the tray water evaporates, water the tray. Only water the soil from above the fly trap if the soil at the top starts to dry out (you want to catch it early).
Apologies if you already knew all that.
Edit: Buying the book "
The Savage Garden" will help you extend the life of your VFT.