Here's what I did. I bought a few of the adafruit boards https://www.adafruit.com/products/127
and then went to digikey and bought the buffer chip, power supply, capacitors and such. I populate the board on what I plan on doing with it. If I have 3v available, I don't need a power supply, if I'm using 3V logic I don't need the buffer. See the trick? In one instance I didn't need the board at all.
However, I did need a minimum of one usb adapter to the laptop and one fully populated adafruit board with FTDI cable on hand as I got into the project. You can get by with the minimum of an arduino and a FTDI with the adafruit board because the arduino can be used to connect to the XBee.
The reason I have the USB adapter is to monitor the working XBees in action. If I want to see what is going on, I plug in the usb adapter and just watch things happen. If a person only has two of them watching one end perform is good enough, with more of them you'll want to see the various interactions and occasionally put something out to simulate something.