you would use oolitic sand as a substrate, with live rock for bio filtration - FOWLR
oolitic sand is basically aragonite sand, adn will very slowly dissolve over the years to help maintain proper alkalinity and pH in the water.
'sugar sized' granuals are preferred...not too powdery, but not too heavy either.
Carib Sea's Aragamax sand is a good choice, but it'll likely run you over $1 per pound, Canadian dollars.
Aroudn here I think I got a 30lb bag for $25US...not much cheaper.
You can try home depot/lowe's type stores, and look for 'tropical' playsand. it's usually around $10 a large bag...as opposed to silica based playsand which is like $5 for 50lb bags.
Brand names to look for are Old Castle, and Southdown. finding them is hit or miss, as its regional whether they'll carry it or not.