The good thing is that as you start wanting to change stagger to adjust to track conditions the air pressure changes you would make also will compliment those track conditions....for example..

When a track is very heavy and fast, you want more stagger...you also want more air pressure in the RR and less in the LR, which will change the stagger the direction you want it to...

When a track starts to go dryslick, you want less stagger, and you also want less RR pressure and more LR tire pressure, both adjustments will take some stagger away.

For a beginner, don't get super worried about covering every combination in half inch or inch increments. You can get by with 2 right rears and 2 left rears as long as they are in the ballpark and measure an inch or 2 different than the other. I currently take 3 of each to the track, but one of each is old and worn out and strictly for using in hotlaps. I have a RR that rolls out to 104" and another that rolls out to 102"...I have a LR that rolls out at 95" and one that rolls out at 96" at standard pressures. That gives me 9", 8", 7" and 6" options at standard pressure, and I can gain another inch either direction or fine tune to the half inch with reasonable air pressure changes...all with only one spare for each side.

If you buy 2 brand new tires the same size there is a decent chance they will roll out as much as an inch different at the same pressure on the same size wheel. If they both end up being the same you can mount one on a one inch narrower or wider wheel and change the rollout. If you have 2 RR wheels with different offsets mount the bigger tire on the wheel with less offset and the smaller tire on the wheel with more offset...because when conditions call for less stagger they also call for moving the RR wheel in towards the chassis, so by mounting your tires like this you can accomplish 2 adjustments with a tire change.

Always remember when you mount a tire air it up to 25# or so and let it sit for awhile. Then bleed it down to race pressure and measure the rollout. A new tire will stretch during it's first time on the track due to heat and centrifugal force and will give you a much different rollout measurement than you thought it had. Airing it up to 25# takes care of that stretching for you and gives you a more accurate measurement.

And as mentioned above, you can grow a tire to an extent by airing it up pretty tight and setting it out in the sun. Just be very very careful not to over inflate it and explode it or the wheel. That can be a lethal mistake. 35 PSI translates to deadly force if a tire/wheel comes apart when somebody is standing over it.

The best way to stay on top of your stagger is to spend a night in the shop mounting all of your tires on different wheels and measuring them at constant air pressures. Use chalk to write the numbers on the tires on different wheels until you find the combinations that give you the most versatility. Once you decide which tires will be used on which wheels write the measurements on the wheel next to the valve stem with a sharpie. This will allow you to just grab one and put it on the car instead of having to measure, think about it and possibly make a mistake in the pits.