I’d go ahead and buy a cord of wood. Winter is just starting and you will surely use it all before winter is over.
This is a tough one, because fireplaces are not very efficient in their present form. Before I installed an insert in mine, we ran thru about 15-20 good chunks a day, and the heat output was lousy at best. Most of the heat in a fireplace is lost thru the chimney. Expect this to be a minimum as you are getting into a lot colder weather both during the day and at night. Don’t forget to inspect and clean your chimney if you haven’t since last year. Bee hives and bird nests will block the airflow. Hope this helps
It really all depends on the wood, hard woods burn longer and hotter than soft woods. It also depends on the size of the fire.
We live in a small 2 bedroom apartment with a small fireplace, we can go through 8-10 pieces in a day, but we have gotten some oak and only used3 in an evening.
Always have more than you tend to use. That way you will always have enough.