I can't find anything on the internet where people actually track object with it other then finding brightest or darkest spots. I need to be able to track a tennis ball.
Paint your tennis ball white or black, and ensure it is the brightest/darkest thing the camera can see.
I wouldn't really recommend the Arduino as an image processor, particularly for someone with no experience of image processing.
Image processing is usually characterised by large data sets, processed very rapidly, neither of which the AVR is very good at.
Get some experience on a more able platform and find out what you need and what you can do without.
Just my two cents.