In order to have a healthy, happy, strong and energetic Bearded Dragon, you must, MUST!!! have proper lighting.
I cannot stress this enough, proper temperatures and Ultra-Violet lighting are ABSOLUTELY crucial (hence the caps).

Lets start with temperatures. Every terrarium should have a gradient of temperature, with a very hot basking spot.

Basking (oF) 

 Warmth (oF) 

 Cool (oF) 

 Night Time (oF)

115 - 110

110 - 90

90 - 84

84 (MAX) - 69 (MIN)

Heat is important because it helps them break down and digest their food. You may notice that every time your dragon finishes hunting his meal, they go to the basking spot. They instinctively know to go get heat in order to help with the proper digestion of the food they just ingested. Heat helps break down food so their body can absorb the nutrition from it properly. But heat isn't enough. Heat has absolutely no affect on calcium. It's great that you can Shake & Bake the crickets and gut-load them, but with-out proper UV lighting, you might as well not provide calcium, and give me the money instead =P.

So let's go over the other lighting needs.

Dragon UV comes in two waves, UVA and UVB, both of which are needed to have that healthy, happy dragon. UV can be obtained from two to three ways depending on where you live. If like me you are in Canada, then it's very rare that you will have your dragon outside since the temperatures aren't warm enough due to the two seasons we have...Winter and Construction ;).

Dragons require, REQUIRE!!! UV to metabolize calcium. Calcium is used in the development of bones and muscles.
Options to attain this UV requirement is listed in this...yes, another table, they are just great and fun to make.

Types of UV 

 Output (nm)