Indeed, especially when starting with affiliate marketing you can use the same domain for multiple offers that you promote. You can create subdirectories on that domain for landing pages and different offers that you promote in order to keep things organized.
Same goes for the tracker, you can use a subdomain for that domain (like trk.TopReviewsOnline.com or start.TopReviewsOnline.com), you don't need to purchase a dedicated domain for tracking.