Diesel Bombers - Gauge Questions from a Newb

My truck is stock at the moment, and I am looking at putting in gauges. More specifically I am looking at the Edge Insight CTS at the moment, but not certain its a better alternative to regular aftermarket gauges. Anyway my question is...

What function does a boost gauge serve?

I understand what it measures, but what benefit comes from monitoring boost. Is it just for troubleshooting turbo/fueling issues? Do you feel its necessary in a stock truck or near stock?

I understand why you would want to keep an eye on EGT, fuel pressure before the IP, rail pressure, and trans temp.

Also what are some tips on using these gauges together? If your rail pressure was low would you see a boost decrease? or what would you see if you had a stuck open injector? Would rail pressure be low? would EGTs go up?

Guess I feel it would be pointless to put all these gauges in my truck if I didn't really know how to use them or what to look for. Any other tips on what to monitor, or using gauges together to look for potential problems?

Thanks in advance!