I'd get a 3d printer as they're cheap as chips these days and play with the printer and cad until you're comfortable. I started with a 3d printer and what I learnt from the printer was enough to start my router build using my own design. I could already cad when I got the printer and the printer in no way improved my cad skills lol but it did teach me about linear motion, slides, etc.

A gantry router and most 3d printers are not so different really, unless you get a rostock or the like.

Learning how to cad is essential for the home enthusiast IMHO otherwise why do you want a cnc controlled machine?