I farmed for Dark Matter to get mine - but I didn't bring out the gui to do it until I'd already five starred 63 of the battles (leaving the last one, which was an easy Juggernaut battle). Once I'd done that, I had already got all trophies bar the one you get for killing a Long Gui and the one you get for holding every weapon/accessory. So basically all I needed to do was kill a Long Gui and then farm Shaolong Gui for Dark Matter, which took about an hour or so and then I had all trophies. I found this a far easier way to do things as it means you don't have to save up buttloads of money once the Gui are activated (and farming them for cash is more troublesome than farming Adamantortoise).