For generating the statistics about new customers per month who made at least 1 order; In my opinion, you should use the filter on the Orders area instead of the Customers area due to the order is created once someone bought something ( at least 1 order). You can add suitable filters to show the group of customers you want.
For instance, you want to filter the group of customers who placed the order in December, on the Orders section, choose Filter-> Select Filter-> Date → Choose the range date and it will show all the results you want ( order number, date, customer name, information, etc).
You can also import all detailed information of customers like email address, country, order quantity, etc to the CSV or Excel file to be easier to analyze by selecting Export on the Orders area.