The Invoices starter solution is one example you can look at. Here's a "stripped down to basics" example of the same approach: http://fmforums.com/forum/showpost.php?post/309136/
Both use a portal to a related "line items" table for data entry so that you can list as many different items sold as needed for a given sales transaction.
Once you have that working for you, we can explore the challenges of inventory management (your additional report).
The White Paper for FMP Novices is useful
Lynda dot com has Filemaker Videos (portions are free)
A free calendar is available to be bolted onto your database
You can search specific Filemaker sites on this Custom Google Search
Looking at FMP business database demos is useful - some are fully useable
The Excelisys Business Tracker V3.0
The Computer Guy, Seattle
Great info from both of you! Thanks, I'll see where it leads me.