Ok well atm I don't do Any racing other than friends and stuff like that, the a-arms, rear axle and shocks help the over all feel of the quad. Not only for track stuff, but for trail riding, and jumping and all of it. If you were to buy some shocks from elka you give them your weight and tell them that the vast majority of your riding is trail riding, and they'll build the shock for woods stuff, and not track stuff. And the main point of gettin a arms, suspension and a rear axle is the wider width stance makes it less tippy and overall more predictable. They also help you in tighter turns and able to carry more speed through the woods. Like I said, when I bought my warrior it had all the stuff on it already. So I'm in the process of buying +2+1 (2 inches wider 1 inch forward, on each arm) elka shocks, and a durablue 2+2 rear axle (2 inches wider on each side). I have yet to set foot on any sort of mx track, I ride mostly woods, w/ some sand, and some jumps.
And as far as the jet's go, it's just to keep your air/fuel mixture at a good ratio, and you shouldn't have to adjust your jets if you don't have any work done to it yet. It's mostly after you put on some performance parts, you'll have more air or fuel in the air/fuel mixture making it run lean which isn't good. If the guy before you had any work done to the quad get the jet's checked or do it yourself, and make sure your not running rich or you could run into some detonation.
So all things considered, I would agree with you on the skid plates, and tires. The performance stuff can come down the line. And when it comes to suspension, it's not just for the racer, but for the person who wants to be able to push the quad and themselves further then the stock set up would normally allow.
I would personally get a feel for the quad in the stock form. So that way when you do upgrade something you should be able to feel how it's working, and if it's what you wanted. Don't forget, if you buy something and you don't like the return it yeilds performance wise, you have a market right here waiting to pick up some spare parts.
~Bill