[Nonfractal]

Jeremy, 

I would make a guess that Chris's porn-box of gears is a retail box from which parts are for sale, maybe at a shop or a club.
C'mon Chris, fess up!

You asked about a "kit" of gears that maybe you should have to hand.
This is a matter of opinion, but this is how I go about it:

Just buy what you need as you need it. 
A box full of crowns is expensive.
Typically, I never buy the crown sizes that come with the cars or kits (Eg slot it yellow SIGI28 or SIGA1628 ) because you accumulate these quickly as you upgrade cars.

As you do upgrades and optimisation on your fleet, you will start to accumulate spare crowns. 

At some point, you will find a need for one of those crowns when  working on another car so the cycle of use and reuse begins.
Some crowns are worth ordering and keeping to hand because they can be used in many cars (eg slot.it inline crowns will fit most inline configurations)
I try to keep one inline slot.it 24,25,26 to hand.

Keeping sidewinder and anglewinder crowns to hand is difficult because the sizing is proprietary and they do not fit all cars.
I keep a few NSR anglewinder and sidewinders to hand but most of these are from cars where I have upgraded the gears. 

Gearing is interesting and challenging but I suggest that you don't jump straight down that rabbit hole with big spending.

Something that has not yet been mentioned is the pinions.
Beware of fitting, pulling, refitting again and again. The friction fit loosens with every refit.
Rough up the motor spindle and use a smear of super glue when refitting old pinions.
When a pinion is so loose that it no longer requires a pusher tool, throw it away.

Again, inline-9 is supplied on most inline cars so I never need to buy one.
(Inline-10 is the factory fit on the NSR 86/89 car, untypical)
Most of my spare pinions are old ones because I only every buy a pinion for a specific job.

Try to be pragmatic.
Gearing is not a golden ticket to the podium.

Seeing as we are in "I'll show you mine" mode ...
It's been a useful excercise to figure out what I have. 

Clearly I have more (factory fit) NSR AW 31 than I will ever need. 
I'll probably never find a use for the "NSR for Ninco" crowns now that our club doesn't race Ninco anymore.