For easier pogramming capability, I suggest a USB gizmo that is
seen as a virtual serial port device, or use a USB to serial
adapter and use a real serial port controlled gizmo for the data
I/O. I'd stay away from devices that require dll based
programming unless you are an experienced programmer.

Serial port programming isn't necessarily any simpler than DLLs.

The labjack device looks to be interesting, and has quite an array of
programming interfaces.