There are loads of different preferences for substrate, firstly ignore calci-sand or anyother man made substrate – do you really want to keep your lizard on pink sand?
Substrate depends on firstly the age/size of the dragon, they are very messy eaters so young dragons should be kept on something like kitchen towel or newspaper, you’ll have to change it frequently so it’s very cost effective and it prevents any issues of impaction from digesting substrate etc…
For older dragons I find that an equal mixture of play sand (not sharp sand/builders sand) and topsoil (not compost etc…) with some vermiculite added to retain a bit of moisture is ideal. I then allow for around 3 inches in the vivarium for them to dig and burrow under logs etc… I can make this mixture up to about 10kgs for less than it costs to buy 1kg of purpose made ‘reptile sand’. Being as the dragons are messy eaters, I tend to feed them outside of the vivarium and with feeding bowls for vegetation. I leave plenty of logs etc… for insects to crawl on away from the substrate. So far I have had no issues, unlike when I tried Calci-sand and had fatalities.
The best substrate I think would be anything that mimicks the habitat of the bearded dragon in the wild as close as possible. It seems odd that a semi-desert based reptile has issues with digesting sand to the point of death, so alot also depends upon what else is in your vivarium I reckon.