So if im correct its 36 long, 18 wide and 36 high?
If so thats not big at all trust me, once full grown they need at least a 75 gallon or 4x2x2 enclosure for a permanent home so I wouldn't worry about how big the enclosure is unless the beardie is easily freaked out by large spaces.
Heating and UVB really depends on the height and where the basking spots will be.
For a Reptisun T5 HO 10.0 tube light the basking spot needs to be within 12-14 inches.
For a Arcadia 14% T5 HO tube light it can be a bit farther away for the minimum distance, around 15-16 inches according to lightyourreptiles.
Personally Id go with the higher percentage, my beardies love the 14% bulbs and seem a tad more active compared to the 10% bulbs, they also are a bit brighter it seems.
You'd probably want a bulb thats 34" with a reflective fitting fixture so then when you upgrade to the 75 or 4x2x2 you wont need to upgrade the fixture.
And depending on where you are whenever petco's tank sales are on you can get a 75 gallon for a fairly good price, around 97 which compared to Petsmarts 200-300 dollar 75 gallon is a lot cheaper.
For a heat lamp just make sure it's bright white light and heats the basking spot surface to 100-110.
You'll have to mess around with wattage's to see what works.
As for substrate you'll want to use tile, paper towels, newspaper, possibly austroterf, reptile carpet maybe, or non-adhesive shelf liner.
This way it has a more NATURAL texture rather than a non natural texture like particle substrates have. Which are not natural for them at all.
Most particle substrates will cause impaction, scale rot, eye infections, fungal infections, joint damage over time, it'll be a prime bacteria breeding ground, sometimes stained scales, and sometimes will cut up the eyes and insides of the animals depending on how sharp it is. Which sadly crushed walnut shells are known to do that.
If you feel them really closely and apply pressure somewhat it'll feel quite sharp.
They come from areas where the ground is hard and mostly dirt, clay and rocks with shrubs and trees around.
A bit like this.