Welcome Jeff! You’ve come to the right place. And here’s a quote from one of the greats on this topic:
Coming from a background in professional detailing and now working for a company that is engaged entirely in surface restoration theres just a couple of things to consider:
The more aggressive the operation the more stress is placed on the pad - heavy correction work beats up pads, so your compounding phases will eat up pads rather quickly, so if you have some pretty serious defects to work on have lots of spare pads.
The more aggressive the operation the more residue management you have to contend with - as you are doing heavy correction work your pad is being loaded up not only with compound, but the byproduct of abrasive actions (clear coat and paint). To remove deep defects you need to remove more material, the more material you remove the more your pad loads up, the more your pad is loaded the less effective it is. Its considered best practices to replace those pads more frequently during the heavy cutting phases.
Keep those 2 things in mind as you decide how many pads to have on hand. At a MINIMUM no one should have fewer than 2 of every pad just out of common sense. If you drop a pad or a pad comes apart you need to have a backup at a minimum to keep going. If you are planning heavy correction work (i.e. - our first full paint correction) I recommend at least 4 pads for your cutting phases so you can at least divide the car into 1/4 chunks and work it that way.
For your finishing work you are doing much less aggressive work, and removing far less material, so 2 pads for your finishing is generally enough. Also consider though - you will do fine polishing work more often as a touchup exercise (at least you should) so if thats the case then having a couple of spares on hand isn't a bad idea either.
The one place I think you can generally get away with 1 or 2 pads is your LSP steps (glazes, waxes, sealants) - its not cutting any material so you have no residue management to deal with, the action is low stress on the pad so no issues there, and in the worst case you can jump to hand application if you lose a pad in the process (not an option in the cutting and finishing phases).
My 2 pennies worth - that and $6 will get you a latte at Starbucks. Cheers!