My experience has been, being as when the 22 first came out there were no spares available yet, that unlike many of the more fragile 2wds on the market there really is no "common breakage" items. These cars are tanks - arguably the toughest buggy on the market.
Now, to be safe, I suppose there are a few things routine to carry for most buggy racers - like front & rear A-arms (though I've never heard of one broken), and a spare wing - just to be safe. But the parts are widely available, so to me there's not really a need to carry a lot of spares. Honestly, I've had my 22's (2-buggies, 22T, and 22SCT) for about 3 years now, and honestly the only thing I've broken is a steering rack (knock on wood). A lot is going to depend on the track you're racing at, and your driving expertise (how fast or slow the track might be, how big the jobs may be, and how often and how big of crashes you're involved in). Some chaps have broken a shock tower here and there, or bent a turnbuckle, but to me this is more of a rarity than common breakage items. A few people lose front axle bolts or rear axle nuts, but a drop of locktite on the front bolts keep these from pulling out and replacing the rear nuts with the aftermarket knurled locknuts keep these from backing off.
The real thing to spend your money on with these cars are some of the common upgrades - like threaded front kingpins and rear hingepins, knurled rear axle nuts, springs, and a selection of caster blocks and steering knuckles - that make it more dependable and easier to work on, and allow you to be able to fine tune the handling to your preferences.
My final word of advice - read the threads here and get up to speed on the car. Literally everything has been covered or discussed more than a time or two. 