So, I've never built a character using tracers. I just didn't, since I thought that they did baseline damage and cost out the rears for the bonus they confer.
But then I really read the description. They're loaded as every 3rd bullet only, (so the cost of 7.5¥/round isn't as bad,) and, therefore, they can be loaded with other types of ammunition. So, loading tracers into a clip with Ex-Ex ammo will provide you with the full dice-pool benefits of tracers, the full damage benefit of Ex-Ex and even save you money in the process. INSANE.
Want to stretch out that APDS ammo that took you months to acquire? Throw some tracers in there. Now you get +1 dice on short bursts +2 dice on long bursts and +3 dice on full auto bursts (for any burst traveling past short range, *Protip: use it in a machine pistol*) and your APDS will last you 33% longer!
Sure, sometimes you've got to keep from being noticed, but other times, you've got to shoot a demonic tree in half with exploding bullets or just tear up the barrens a bit. In these cases, tracers = win.