Beardies grow fast and it will probably be close to full size in roughly 1 year. you will need a 40 gallon breeder minimum for it as an adult however it can be kept for roughly 6 months in a 20 long before graduating to the larger size.
sand is ok to use with these guys IF you keep them at the right temps.... basking spot of 105, cool side mid 80's. I would highly recommended play sand over "reptile specific" sand. it is the exact same thing but the reptile sand is in a smaller bag and costs more. Calcium sands are really useless and seem to cause more problems than good...also they are not quite as fine as play sand and tend to clump easier.
you NEED a UVB and a heat bulb. you can get a combination bulb that does both but these are pretty pricey. UVB is absolutely essential for proper bone growth so do not skimp because of the price.
a temp gun would be a very useful tool so you can measure the surface temparture of any given area... dials, sick ons an dother thermometers only measure the ambient temp of that area..... to get an accurate basking spot you will want a temp gun
feed crickets, meal worms and a variety of a veggies. NEVER ice berg lettuce. avoid lettuce all together really, dark leafy greens like collards and mustard greens are best. you can give them some things like strawberries and peppers as treats but not as a daily thing. avoid spinach and cabbages.
If it eats it's greens pretty good then it probably will not drink water at all often however you should always provide a water dish just to give them the option.