Cloud tracker with a genuinely usable free tier for new media buyers.
BeMob is the tracker to start on. The free plan is not a crippled demo: 100K monthly events, 10 campaigns, real landing-page and offer management, and reporting good enough to learn how postbacks and tokens actually work. For a buyer validating their first funnels, that is the right place to make mistakes before money is on the line.
Paid entry is cheap too, at $49/mo for 1M events, and because it is cloud-hosted there is nothing to install. It is the gentlest on-ramp into tracking of anything here.
The limits show up quickly once you scale. BeMob counts every impression, visit, click and conversion as an event, so that free allowance vanishes the moment you run impression-heavy traffic. Custom tracking and cloaking domains, which serious buyers need, only appear on the $249 Business plan. Treat BeMob as where you learn and test. When your spend justifies it, most buyers graduate to RedTrack or Voluum for the extra depth.