Battery Cycles being used very fast

I am using a 13-inch mid 2014 MacBook Pro with Retina Display. It is about 3 weeks old and already has clocked 13 charge cycles. Is this too high ? Also, I follow the practice of fully charging it and then using till about 40% before recharging without ever leaving it plugged in. Is this the best practice to follow or should I leave it plugged in while charging ?

Thanks