here is a quick list of some good leo breeders:
www.acreptiles.com
www.crestedgecko.com
www.hisss.net
www.goldengategeckos.com

slate or tile will work best for substrate. moss isn't usually used in leo enclosures except for humid hides/lay boxes and insects can easily hide in it making it hard for the leos to eat and hard for you to regulate feeding. carpets get stinky and gross fast and it is hard to really disinfect them well enough.

i dust with rep-cal calcium (phosphorus-free with vitamin d3) and rep-cal herptivite. a dish of the calcium should also be available in the enclosure at all times.

i only use flexwatt for heating leo enclosures. the only reason to use a heat lamp is if your temps are too low without one (cool side 78, warm side 88-90 degrees) or for viewing purposes (in which case you can use a flourescent bulb with will last longer and doesnt' put off heat).