Before you buy camber plates, you need to figure out if you need them. Tire wear is one way to measure, but is probably the worst indicator. The best is a tire pyrometer. Like this:
Basically, go out on track and drive normally. Do not do a cool-down lap. Come straight to the pits and start taking temps - do inside, middle, outside. Get a friend to write them down so that you can take temps faster.
Not only will doing this tell you if you alignment is right, but also if you pressure is right. Ideally, you want the inside to be even across the tire. But, variations of 5-10* is probably what you will see in the real world.
Temps - Inside - Middle - Outside
Ideal - 130* - 130* - 130*
Real World - 125* - 130* - 135*
If you see your outside between 10-20* more than inside, then you need to see about a little more camber. More than 20* means you need to get a LOT more camber (well, "more" negative camber).
If you see your middle temperature is not inbetween the inside and outside, it means your pressures are wrong. If the middle is higher than either, you have too much pressure. If it's lower, you need more air.
This is a good article to start with. And, use the tire manufacturer's specs for tire temps - not the car.
http://www.turnology.com/tech-storie...for-the-track/