Many of the networks will have builtin tracking software. You upload your image and they take care of hosting it and tracking it. On other websites where you are just providing the html code, there is another way to track.
I use this tracking service:
It has a 'banners' section that lets you create a single banner html code that will rotate and track an unlimited number of banners.
So you just load up every campaign you have into this tracker, then promote the 1 banner html code on various places and check back in a few days to see which banners are giving you the most clicks and which traffic sources are sending the best traffic.
You should now have an offer and some advertisements to promote it with. Next you need to start buying traffic and banner impressions. The left column of this page under 'Advertising Networks' shows you where you can start doing this.