Sounds like you are trying to calculate first occurrence.
See if either of these posts help in explaining how this is done. There are some very helpful ninjas in these conversations that helped me build a similar view.
Do you have a particular mock-up/view in mind? It would be helpful to see a packaged workbook with the methods you've tried first. Cheers.
Here's some additional links that may help:
Thank you Mark and Matthew. Basically, I'd like to be able to do these actions completely inside Tableau.
1) Get the result of executing this SQL query:
CREATE TABLE first_order AS SELECT "Customer ID", MIN("Order Date") AS "First_Order_Date"
FROM Superstore_Subset GROUP BY "Customer ID".
2) Now put "First_Order Date" as a Continuous Day on Columns and COUNT("Customer ID") on Rows, and use a continuous line to connect the points.
The closest thing I could find among the examples was Mark's last example (Count First Time Customers by Month), but for some reason when I tried following the method in that workbook with the Superstore_Subset data, things didn't go as I was hoping.