Add each column to the Pivot Table again (Revenue, Length, Days, etc.).
Then, using the "Field List", left click on each of your new columns to access the "Value Field Settings". Click the tab that says "Show Values As", and scroll down to "Rank Largest to Smallest".
This will assign a rank to each value in the column. Smallest to Largest is also an option if that is more appropriate (maybe "Days Since Purchase" should be ranked this way for example).