You can buy chick starter in as small as 5 lb. bags. You'll be surprised how fast it goes. The idea of the starter is to supply what they need since they aren't with a mom to tell them what, and what not to eat. I'd stick with the chick starter to be safe....
I have used everything from rusks to oven-toasted and crushed bread to sesame seeds and desiccated coconut (or all of these mixed together). I have used these mixes for several days as I live a bit of a way from the poultry supplies store which is not open at the weekend. They seem to love and thrive on the mix.
Though chick crumb is designed for the purpose, chicks have survived for hundreds of years before such things were made.I do agree with a previous posting, though, chick crumb is available in small bags. As they are ravenous little creatures they go through a lot of food in a few days,
Chicks can and will eat their starter for the whole time that they are growing, so you will use it up. They are growing so fast that they need a good feed during that time. I free range or tractor my chicks on grass, sometimes as soon as 4-5 days old, but they still eat a lot of food - that tells me that they must need it.