In the attached pic you will see everything I used to build a CNC Mill. You need a driver board, power supply, stepper motors software, a computer and that is it.
I used a Xylotec driver board which cost $85. There are a number of different boards available. Each stepper motor connects to the driver board and the driver board connects to the computer via the printer port. Mine is down stairs engraving a sign as I write this.