Which legendary Bird are you spending your rare candies on?

Pidgey

I put a little bit into Articuno, up to 1830cp...it matches up with a Dragonite in battle (they about zap each other)...problem being: Dragonite matches up with most everything else

Articuno for dragonite when it releases as a raid boss and zapdos as a stronger electic type + it hits super effectively on all the birds but itself which it still hits neutral

Dragonite.
For the real legendary birds, none.