Well as far as GC treats go, Quito just absolutely adores littles pieces of green grapes. You have to sort of limit them to maybe one whole grape per day though, or else they'll start doing their Lorrie poop-shooting imitation.
I can get about 12 pieces out of one grape. Little chopped up pieces of (bird safe) nuts would also go well with Quito. I think its harder to treat reward a small bird, because you have to watch how much you give them so closely. She also likes chopped up dried mango but usually chews off a little bit and then drops the rest, so not very suitable for training.
Haven't tried clicker training myself, but have read many good things about it!