You'll get a ton of different answers to this. For getting familiar with your AP3 I would monitor Octane Adjust Ratio Learned, Oil Temperature, and all four ignition corrections. The OAR monitor should settle out to -1 if your fuel is good enough for the map you're running, and when it does you can change to something generic like AFR Actual. Oil Temperature is inferred, but it's going to be a relatively accurate gauge to tell you when it's safe to go full-boost because you don't want to put that kind of load on your engine when the oil is cold and not flowing well. The ignition corrections will tell you if you're adding timing or having it removed, and if you're having it removed (negative corrections) you'll want to datalog and find out why. Once you've put enough miles on you should be able to see trends with it and determine if you have a weaker cylinder or not. If you have one that statistically reads lower than the other three you can remove the other three from your gauges and only monitor the one.
Once you get more comfortable using it you will probably want to mess around monitoring different monitors, but that will happen in time and based on whatever your current needs are.