If you have all the basics, then a really good pair of shorts and a nice jersey. They are my uniform for long rides, and make more mileage possible. You might as well look good when you're all sweaty and spent.

Or a camelbak or polar bottles
Garmin 305 or something with HR, cadence, mileage and speed
Do you have a rack for your car?

The only tools I have are the basics for my saddle bag--she visits the boys at the shop once a year for everything else.