For templating thank-you pages and emails, note that there are differences in which [%template_variables%] will work in the Common page, Common email, Product-specific page, and Product-specific email -- each of those has its own section here:
In particular, note that most variables pertaining to a particular product -- such as [%item_name%], [%item_number%], [%item_price%] and [%quantity%] -- can only be used in a Product-specific thank-you page or email (which you would specify in that product's own config screens), and will not work in a Common thank-you page or email (configured in your Admin > Account Prefs screen).
BTW, if you configure a Common thank-you email template with the [%thankyou_link%] variable, that will insert a link to a Common thank-you page where the actual order details (products ordered, etc.) would be itemized along with any download link(s) for digital products purchased in that order.
EDIT: Corrected template variable to insert Thank-you Page link.