Well, I've only changed his food once after we got him - we just thought he didn't want to eat much. We only changed his food because we thought it was better quality, and then when we saw him start to eat more, we realized he probably just didn't like his old food. Now he's back to eating minimal amounts of the new food unless I mix something in with it. He's an 8-pound dog and only eats about 60g (1/2 cup?) of kibble on a good day.
If you’re going to stick with kibble... This might sound totally weird but try this: mix some lukewarm water in with the kibble so it becomes “soupy”. I’ve known many dogs where this did the trick!