I never actually heard of a 7% UVB bulb, most I have encountered are 2.0, 5.0, 8.0 and 10.0%. The higher the percentage the better as that measures just how much of the light produced by the bulb is UVB. I recomend getting one that is at least 5.0%, with higher being better.
You mentioned a kit you saw at Petco....what else does it include? Half the time the stuff these 'reptile' kits contain are junk, harmful and unsuited for reptiles. Things like heat rocks, calcium based or crushed walnut shells for substrates (both cause a high risk of impaction, especially with baby dragons, in the case of the crushed walnut, they can also damage the lining of the intestines as well), the therometers are also mostly ineffective or inaccurate (the dial ones and strip ones especially. A digital therometer with probe is best to buy) and also, the overall cost for these kits, makes its not worth it, since most of the stuff shouldn't be used anyway. From the petstore the only two things you really need is the tank and the UVB light. Everything else can be purchased much cheaper elsewhere. THings like feeding dishes (small ceramic bowls, 2-3 for a dollar, depending on size), small flower pots with holes cut out of the side for a hide or just a piece of driftwood that has sufficient space underneath can double as a warm side hide and basking log (make sure it is sturdy enough so your dragon can't tip it over or have it fall ontop of him if he digs underneath). Heating/basking lights can be regular household bulbs and flood lights. Digital thermometer with probe and even a hooded light fixture, can be easily found at Home Depot or Walmart for a fraction of the cost they would be at a petstore.
Crickets can be ordered in bulk through the mail or even through local breeders/suppliers for much cheaper than bought at a petstore. Some petstores, however may allow you to order 500-1000 at once for a cheaper price (not that I have seen it so far...would cost me about $40 for 500 to get it in bulk at my local petstore...I can get 1000 for half that price via mail order).
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PHLdyPayne