In your "Swag" table, add a count field that tallies the number of linked records (or rollup field if it's something more complex than pure record number), then you can lookup that field in the table that's feeding your interface. In your interface you can add a simple filter to only display records occurring more than once or twice, and then sort your x-axis by descending, which will clean up that graph a lot.
On the 25% off, that's tougher. Maybe there's a script out there somebody has, but I'd say you don't track information in that manner. They ordered the same item, it should be named the same, with the 25% expressed in either a separate transactions table, or perhaps some kind of sale select field which impacts the calculation of your total due.