Flowers are good, and so are the balls, they bounce them on their heads. :3 But the Jack-in-the-box scares your Tama, and I hope you knew the Dung was a bad present. I'm also new to tamagotchis, so those are the ones I've encountered.
The only "bad" presents are poo, sickness, ghost, and jack-in-the-box (unless there are more that I'm forgetting). All of the others will make your tama happy :]
Also, after the two tamagotchis become friends, they should stop giving bad presents.