Your layout should be based on InvoiceLine. To filter by date or other criteria perform a find specifying that criteria. you can also use Go to Related Records starting from Invoices and can constrain found sets produced by Go to Related Record or previous finds to further refine your selection.
You can use sub summary layout parts to produce sub headers and sub totals or even to "condense" your data so that each row of data in your report represents a group of InvoiceLine records instead of a single record.
See this tutorial: Creating Filemaker Pro summary reports--Tutorial