One aspect of the pet bearded dragon's husbandry that the keeper SHOULD NEVER cheap out on is it's source of UVA & UVB lighting.
You really have only a few choices
1) if the climate is suitable ( similar to their natural range wrt temperatures, RH, UV and daylight hours ) keeping the pet bearded dragon in an predator and escape proof pit or converted (bird) aviaries where the dragon can experience natural sunlight is BEST.
2) if the dragon is housed in a tank in side your home you will need a to provide adequate levels of both UVA & UVB , and UV flux gradient from very high levels to very low , and sufficient time each day for the dragon get the needed dose of UVA & UVB for it's needs.
so you need
a) Smaller tanks
a very high quality compact fluorescent source ( only brands that provide these with good UV spectrums are Arcadia , Exo Terra and Zoo Med., go for a 10% UVB compact rated 25W , these work well in very small tanks where the basking spot is about 8" from the tube , BEST solution is NOT a dome style reflector, I've had excellent results for bearded dragons using horizonal mounted reflector hoods such as Exo Terra Nano Hoods which give a nice spread of UVA & UVB ( I've measured these using Solarmeters and mapped it ) sufficient to cover the width of a 120 L tub and most of the floor of the tub.
b) larger tanks a good options are
>> a MVB ,these are an all in one heat, light, UVA & UVB source BUT can't be dimmed and can be hard to fine tune both the thermal gradient and the UV flux gradient. Gives a narrow focused beam of UVA & UVB , so most supplement using another UV source in parallel
>> or a MHB , these are not very common and pricey , but are also an all in one solution with similar restrictions as a MVB but I believe are dimmable using special circuitry.
>> or a T8 or T5(HO) UV tube , best brands are Zoo Med , Arcadia and Exo Terra UVB tubes (these actually produce nice UVA & UVB spectra.
The rating of the T8 or T5 HO tube depends on
- the tank height
-- the tank width
-- will it be placed under the lid (best !) , or on the top of the back wall , or on top of a mesh lid
.. how fat the basking spot will be from the tube
In general aim for UVA flux ~ 1 milliW / sqcm and UVB flux ~ 180 microW / sqcm @ the basking spot.
In most situations this is only achieveable using a reflector hood where the reflector is parabolic shape designed to focus the UVA & UVB
Aim for the tube to be about 2/3 the length of tank and mount with one end near the basking globe.
The UVB rating recommended for a tank about 2ft tall is a T5HO tube with UVB rating between 10% and 12%.
Avoid cheaper brands , they are cheap for very good reasons
> poor quality silica glass used ( will leak nasty UVC )
> poor quality phosphors used ( with very poor UV spectra , can and often do cause eye problems for the reptile )
> poor build quality ( often don't even last a week before dying where the better brands are guaranteed to work to specification for 6 months , Arcadia for 12 months )
so they are a false economy.