Push ups are an excellent exercise to build great chest. I recommend first find out how many push ups can you do at a stretch be it 15, 25, 30 or 45. Then try doing at least 20 push ups in each set and do 5 to 6 sets.
Once you have accomplished that try doing more sets say 8 to 9 gradually over period of time as you build strength and become stronger. Then on increase reps in sets say to 30 and cut down on sets. Usually higher the reps better because it's a body weight exercise. over a period of 3 months you should see some good results.
Hope this was useful, for more update on training routines, Training videos and dieting strategies please subscribe to my channel.