Well first off, disregard everything the pet store employee told you. Pet stores aren't known for their good advice. I'll post my care sheet below that I've made over the last six years of having my beardie. I'd recommend reading the care sheet, then returning everything you bought at the pet store to buy the correct stuff.
Live Prey
Silkworms (Best), Phoenix Worms, Crickets (Gut Load and Dust) or Roaches (Dubia or Lobster to name two). NO mealworms. They are high in phosphorous which binds calcium and can lead to MBD.
Superworms and Waxworms are both considered treats. They should never receive more than 3 or 4 a week as they are very addictive and very fatty. And never to any dragon under 16 inches.
Mice or anything else alive, or frozen, should never be fed to a dragon.
Veggies - Best to combine a few to keep it varied.
Alfalfa Plants, Bok Choy, Cactus Pad/Leaf/Pear, Chicory, Collard Greens, Dandelion Greens, Endive, Escarole, Mustard Greens, Swiss Chard, Turnip Greens.
Fruit - Once or twice a week treat, NO Citric.
Scallop, Summer or Acorn Squash shredded over the veggies.
Dusts
Calcium - Rep-Cal Phosphate free with D3, Absolute Calcium, Minerall, Calypso.
Multivitamin - Rep-Cal Herptivite, Reptivite
Feeding
Juveniles - 80% Protein 20% Greens. Feed as many crickets as they can eat within 10-15 minutes, 2 or 3 times a day. This should add up to between 40 and 200 crickets per day! 6 days a week dust one feeding with calcium (D3, phosphorous free). On the 7th day dust one feeding with a multivitamin. Greens should be available all day from waking up until 1 hour before lights out.
Adults (18 months) - 80% Greens 20% Protein. 20-50 crickets a week. Calcium dust one week then a multivitamin dust the next week.
Crickets should be no larger than the space between the eyes of the dragon. And never leave crickets in a habitat with a dragon after feeding is done. They cause stress and can seriously injure a sleeping, or even awake, dragon.
When feeding crickets you must wait at least one hour after lights come on to feed, and 2 hours before lights out should be the cut off for feeding.
Housing
0-12 months - Minimum of a 20 gallon long.
12+ months - 36”L x 18”W minimum. 48”L x 24”W is better. 18” to 24” in height.
Humidity
Bearded Dragons are a desert dwelling reptile therefore require no humidity. They get their hydration from licking it off their surroundings. The best way is to give them 10-15 minute baths with a water temperature of 90-100 degrees Fahrenheit 3 or 4 times a week. Water should be no higher than shoulder level. If the dragon freaks out put a cloth or something in with him to give him purchase. Baths also help during shedding, so you can increase baths to a daily thing during sheds to help with them.
Substrate
Any non particle substrate is advisable to use for any size of bearded dragon. Using a particle substrate can lead to death due to impaction and also bacterial infection. Paper towels, Reptile carpet, non adhesive shelf liner or my personal favourite, coarse ceramic tile are good ones. Tile should be baked at 250 degrees in the oven for 15-20 minutes to kill all germs and bacteria. Just wrap it in aluminum foil.
Heat/Lighting
Bearded Dragons need a hot and cool end in their habitats. The highest point in the hot end should have a SURFACE temperature of 110-120 degrees Fahrenheit and the cool end should be about 75-85 degrees. An infrared temperature gun is best for measuring surface temps. Just point at the surface and click for an accurate reading. Can order one from http://www.tempgun.com/main.html
For UVB they will need a fluorescent ReptiSUN 10.0 UVB tube light (the best tube light on the market). They should be able to get within 4“-6” of it without being able to touch it in case of burns. And it should not be filtered by a screen or lid. Mesh lids are okay though. Coil or spiral UVB bulbs are not good. They have been proven to cause damage to lizard's eyes and even gone as far as burning them.
For a basking light you can use a clamp lamp with a halogen flood light bulb. Be careful with wattage here as the halogen flood lights give off more heat than a normal household bulb of the same wattage.
Cleaning
For cleaning the dragon’s habitat use baby wipes and dry with a paper towel for spot cleaning. Once every month completely clean the habitat and all ornaments/food dishes with a steam cleaner, if you have one, or with a lemon/water solution if you don‘t.
If you have any other questions, feel free to edit or ask, or drop me an email.