You're probably better off just buying them. Getting a craft to 50 is relatively easy enough. But getting the tool and materia melds to hit the 3 star reqs is a pretty major undertaking that's sure to cost more than just buying the fighter augments.

And if you can't buy them I'd recommend armorsmithing, weaving or leatherworking to 50 instead and devoting a retainer solely to selling glamours. That's steady cash to save for augments or getting a craft 3 star ready.