Programmer /Debugger for freescale kinetis series
Option 1: FTDI based adapter and OpenOCD (eg. from Olimex)

Option 2: K64-FRDM board has built-in JTAG, that you can connect to an external board (it is fully supported by Kinetis Design Studio).

Option 3: get a SEGGER J-Link with EDU license. It is much cheaper than the commercial version, but you can use it only for education/experimenting.

Personally I love using SEGGER tools to make a living, they work fast, they work reliably, every single time and it takes very little time to set up the drivers. J-links also support RTT which basically is a "serial terminal" over JTAG, so you don't have to expose an UART on the PCB for debugging.