The chick starter is all new chicks need. No need for extra calcium or to give them grit. Once young birds go outside and you give them treats and table scraps you should give them grit if they don't have dirt under them to get their own.
The thing about grit is it aids in digestion but it not essential. What happens if chickens don't obtain enough grit is they don't break down the harder parts of food intake so simply eat more food to compensate. Grit should not be more expensive than your added food cost without it. It defeats the purpose. What I'm getting at here is it doesn't need to be granite and certainly don't purchase those small granite bags. Grit (crushed granite) can be purchased in bulk, by the pound, from your local feed supplier. It's incredibly cheap that way. And if chickens are scratching up a storm in the dirt I assume they are finding their own small stones like nature intended. But then again, by nature's plan they'd be eating hard berries and nuts and seeds for nutrition and that's why they'd need small stones to grind it up in their gizzard.