At your level in table tennis, fitness might not seem very important.  However, if you want to improve 2-3 levels, fitness will become an important aspect of your game.  Prepare for improvement!  Avoid injuries!  Increase your speed!  Boost your endurance!  At the end of every training session, do 20-30 minutes of intense physical training focusing mainly on foot speed, core strength, stability, and balance.  
I thought about making a video with the 10-15 exercises that I do on a daily basis.  However, I ran across this awesome video including some of the exercises that I do plus many additional ones.   Start with the easy ones in this video then build up to the difficult ones.  
http://www.youtube.com/watch?v=POdzasJklxw