I advise against dry firing any guns. It puts different stress on the firing pin than it was designed to put up with.
The deceleration of the firing pin is slower when it hits the primer VS stopped by the body hitting the frame. Also the pin that normally strikes the primer sees a negative force rather than a positive force when dryfiring.
Will several hundred times hurt a gun, no. Several thousand, who knows. But if you’re going to train, or build up your trigger finger buy some snap caps, much cheaper than replacing the firing pin. The other advantage with snap caps you can load them in the middle of a magazine and practice clearing a failure.
9mm, package of 5, 12.99$.
http://www.midwayusa.com/find?userSearchQuery=snap+caps