CaptainX

*100 donation pokemon later*  

Well I'd try to get the rarest pokemon, so shoot for a mystic or metallic Meloetta. Others would just get the coolest looking one, so it really depends. If you're getting one for you, get the coolest one. If you are getting one to trade, get the rarest one. (I haven't actually donated fyi)

@Mark Thompson Yeah. Just pick what you want. Correct me if I'm wrong, but Mewtwo Armors are the most common, so anything other from those should be a decent investment.