You may as well just buy some Lego Technic because it will cut just as well this machine and you'll learn more with the Lego.!!

All that buying cheap stuff learns you is how to waste Money.!! . . . . If you want to learn then read all the build threads start to finish, then read them again.
You'll get more info from these than you will wasting money on rubbish.

Wiring and setting up drives, motors etc is much easier when you have done the research. As is building a machine because you'll be well clued up on whats needed and if read careful should avoid some of the pits falls.

In the time before you start building and during the build you'll be well advised to invest your time in learning the software, Mostly the Cad/Cam side.
The Controller side ie Mach3 is what often scares people but in reality Mach3 doesn't do anything other than Control and monitor the machine.! After it's setup so it's talking to everything then the actual using of Mach3 to cut parts is really simple and basic.
Setting up Mach3 is easy enough and again if done enough research then you'll have learnt quite a lot about whats needed and the rest just ask.!

The using of mach to cut parts basicly boils down to positioning tool at a point on work material which you establish in Cad/Cam as being Zero and Zeroing each Axis. Then you Push cycle start sit back and watch it happen.!!! . . . .Simplizzzz.

All this can be can be learnt and simulated without having a machine. So why waste good money on junk. Save the money and read everything and you'll have a real Cnc machine sooner.!! . . . And you'll know how to build and use it.!!