First thing, I drift the rear sight out and install it backwards so that it shows black instead of a white outline. Second thing is to install a Ghost Edge connector. The third thing I will do is install Vickers base plates on the magazines. Those things are mandatory.
Eventually, I will possibly replace the slide release with a Vickers. If it’s a range gun, I will also replace the slide stop with an extended version.
On some of my pistols, I have splurged and installed a steel rear sight and a Ameriglo front square night sight. That’s definitely in my category of ‘nice to have’, and not ‘must have’.