Desktop size build to learn on - PCB routing / small MDF work.

[Neale]

Remember that if you chase up JGRO information it's usually from a US site (such as CNCzone) and there are a number of things that the US tends to do differently. Mainly, this seems to be avoiding anything that is sourced from China in favour of good ole US of A manufacture! So, they tend to use threaded rod on smaller machines and rack-and-pinion on larger to avoid ballscrews; Gecko drivers rather than the Leadshine or similar; various guide bar systems such as the skate bearing style of thing in place of profiled rails. They tend to use routers quite a lot as well in place of the ubiquitous Chinese spindles. People seem to have built the JGRO design with little more than a cordless drill, jigsaw, and the kitchen table, however. You might also look at the Joe's 2006 design which is a much-improved version of the JGRO but really needs a CNC router to make the components. It's all a bit Catch-22 here!
I'm almost certainly in a very small minority (might even be a minority of one) on this forum by actually building and using a machine in MDF. There are very good reasons for avoiding MDF! However, you could probably halve the cost of the electronics by choosing lower-spec components, as mine are definitely OTT for the machine I have, and that might make it an accessible "starter" machine. I'm sure that you would learn much more than going out and buying one of the Chinese aluminium-framed machines, even if they are probably more capable.
Just as an indication, I've profiled and engraved an oval 400x300 hardwood plaque for a presentation, engraved reasonably fine detail in a small jewellery box lid, profiled 30mm thick curved sapele rails for a new hatch for my boat, and done 3D carving, all on my machine. I'm currently playing with an idea taken from the 'net for a cable chain cut from interlocking pieces of MDF, to be cut on the router. I haven't tried making PCBs on it yet, but I think I probably could, and shall probably have a go at it some time. Toy? Absolutely, compared with the machines that most people here have built, but not too expensive, not too difficult to build, and great fun into the bargain. Needs a biggish desktop, though - my machine just about covers a 6'x3' bench.