If you are getting chicks this spring, they will not need grit if you are only feeding chick starter. Any time you add other things to chicks diets, you will need to add grit. Parakeet grit and gravel is perfect.
As for pullets or adult hens. If they are free ranging, you do not need to add grit. They can find their own. If you don't keep them on sand and they are confined, you will need to add grit. You can get small bags of poultry grit from
Manna Pro. Most feed stores carry this grit.
Do not confuse grit with oystershell. Two different things and oystershell should never be fed as grit. It is only for the hens in addition to their layer feed. If they need more calcium, they will pick thru it. Do not crush it. They can pick thru it just fine.
Oystershell needs to be available at all times. You can keep it in another feeder or small low tub of some sort.
For 6 hens, you will need at least 2 nesting boxes. 1 is not enough and there will be fighting, broken eggs and waiting lines.
Great to have you aboard and enjoy your new babies this spring!!