30 items is a lot to show on a line graph, but if you grouped the items by categories, a line graph might work just fine, then you could drill down to see the items within each category on a separate graph--or if there is a hierarchy established, you could drill down from Category>Item in one sheet, but you'd end up with a lot of marks for all the items.
The attached workbook (version 8.1--let me know if you need a Version 8.0 example) shows an example of this. I used the "sheet selector" method shown at the link below to collapse the bottom sheet down when no selection is made, and that sheet will pop up when a category is chosen from the top line chart.
Note that not all items had sales in every month for the year shown, so I had to connect the lines using the Formatting option for the Sum(Sales) pill:
I hope this helps you figure out what you want to do!