Hi kidsteeze, welcome to BD.org.
As has been stated above, you'll probably want to do some research on dragons, now that you have one. The Zilla snake kit comes with a couple of things that you will need, but you'll want to check out this shopping list. Bearded dragons, especially younger ones, are not the cheapest of animals to raise. For starters, I'll lay out what you will want to have.
First off, I would say if you can return the snake kit, do so. If you have a Petco in your area, they are having a dollar per gallon tank sale through the 18th of September. 40 gallon breeders are the minimum size of tank that an adult bearded dragon can live in. So, with the sale you're looking at spending about $40 on the tank, $25 on the tank lid. For the substrate, the easiest thing to start off with is plain paper towel or newspaper, that way you can keep track of your dragon's bowel movements. You can look into other substrates such as slate tile, carpet, or shelf liner also.
Now, for the lights... this is part of the biggest expense of a dragon. For a 40 gallon tank, you will need at least one basking light, if not two, to maintain proper temperatures. I would recommend getting 2 8.5 inch ceramic light fixtures
http://lllreptile.com/store/catalog/reptile-supplies/light-fixtures/-/zoo-med-regular-black-ceramic-clip-lamp/ . For the lights, you'll want to get either your reptile lights they sell at the pet store, or you can get halogen lights from walmart. You will also need a thermometer, most of the people on this site have found that the Accurite digital probe thermometer (also available at walmart) works best for keeping temps. I have found that for a 40 gallon tank that a 100 watt basking bulb on one side and a 40 watt bulb in the middle keep good temps in the winter, which is fast approaching. You'll want to gauge your own temps, everyone's varies. The temps for the tank should be, as was stated above, 100 to 110 degrees basking, no cooler than 75 degrees cool side, and about mid 80's for the average ambient temp.
The other light that you will need is a
UVB light, something like this one is preferable
http://lllreptile.com/store/catalog/reptile-supplies/uvb-fluorescent-lights-mercury-vapor-bulbs/-/zoo-med-24-repti-sun-100-fluorescent-bulb/. All that you need in addition to that is a flourescent light fixture.
The other part of owning a bearded dragon that will get expensive is the food. Bearded dragons are omnivores, and you need to supply them with salad daily along with insects. You will want to feed crickets out of the cage, as free roaming crickets have been known to bite and kill young dragons. The salad should consist of dark greens such as collard greens, mustard greens, endive and escarole. A full food chart is available at this link
http://www.beautifuldragons.503xtreme.com/Nutrition.html, I highly suggest reading it over before feeding your dragon. For the protein side of the equation, plan on feeding as many crickets as your dragon can eat in about 10-20 minutes 2 times a day. The bigger your dragon gets, the more it will be eating. There are many forum threads and articles about insect food choices, again, I would recommend reading them.
Other things you will need are some form of a basking surface, such as large rock or branch. If you bring it in from outside, MAKE SURE that beyond any measure of doubt it is completely cleaned and sanitized, a process that typically involves bleaching and baking. You will probably also want some form of a hide, and if you have an old light timer, that will make it easier to keep your dragon on a 12 hour lights on/12 hour lights off photoperiod.
So, here are the figures, not including food.
Tank and lid-$65
Light Fixtures- app $25-30
Lights- app $10-20
UVB light and fixture- anywhere $40 on up
Thermometer- $12
Accessories- factor in anywhere from 20-50 dollars, depending on how much you like decorating.
If you have any other questions, just post and someone will be able to answer.\
~RK