Honestly I think weighted pushups are one of the best exercises you can do for you upper body. If you want to "tone" of build muscle you probably need to do 8-12 reps to failure (you can't do another rep with good form) if you can't add weight just do as many reps you can. You don't need that many sets 3-5 sets a day can be all you need.
Wgen you train your chest also keep in mind that you need to do the same or more work for your back. Or you risk injury and bad posture.