Dear DJ Ron,
I'm in the process of building my audio library and putting together a DJ demo. Also, I plan to purchase a Mac laptop and Traktor (or maybe Cue) software.
What do you consider as the "industry standard" regarding audio file format: mp3, mp4, m4a, or wav?
For audio files, 320 bit mp3s or WAVs are standard. Most average people can't hear a difference, so unless you are playing really big rooms with massive sound systems, it won't matter. But this may be a question you have to decide for yourself over time, depending on your own aesthetics.
mp4 (short for mpeg 4) files are usually video files and is the standard for Serato software with video plug-in. Other video programs, such as Cue/Virtual DJ, can use mp4s along with mpeg-2 compressed files (vob, mpg), avi, Quicktime (mov), etc.
Good luck with your entry into the world of Digital DJing.