I've had sulcata - a rescue I eventually re- homed. The most common mistake I see with babies is too much of something they seem to luv. It's like with your kids. If you asked them daily what they want to eat they would fill up on chips, fries & McDonalds. Not good.
Variety is key
As well as water , soaks , and a place to rest with various temps (90-70f) and sunlight.
A calcium supplement like chopped up cuttlebone is important ( be sure to scrape off glue on back of cuttlebone first)
If in a small enclosure like a tank - he will need exercise to build leg strength for that eventual big shell. Take him out and let him walk - with close supervision. Dogs & cats will chew them unsupervised. And Don't forget even the little ones can dig out of enclosures
Good luck.