YES! 30% GBS is the best thing you can feed your quail! Everything else is supplemental, or a treat. I agree with twocrowsranch about a dustpan. I consider it a MUST, not a treat or something they need to stop mites. It works off excess energy, and is even a social event for your birds. There isn't a mite closer than 37 inches to my birds, but the do love their dust bath!
Nutritious greens like kale, collards, turnip, mustard, spinach, etc... Pretty much any high nutrition high calcium greens are good calcium supplements.
If you can feed any of these with regularity, then you don't really need oyster shell. (Most species of quail) especially coturnix are champs at absorbing calcium from their diet. They don't need to eat a bunch of oyster shell like chickens or other galliformes.
This is my opinion of things/feed/treats one should avoid.
Iceberg lettuce (PURE EVIL!)
White Bread (PURE EVIL!) Pretty much anything that is made into a bread like thing. Including, but not limited to...cakes, muffins, fritters, etc.... Even "Whole grain" versions of the same.
Pasta (Pure Evil!)
The jury is still out on cooked rice, but maybe in moderation....
Anything dried that expands to 2 or more times it's size when exposed to tap water. Dry beans, rice, pasta, grits, etc... It's a "No Brainier" and not trying to insult anyone's intelligence! Just covering the bases here.