1: Amount of times you hit 2+ enemies with the champions ultimate
_(replaced with something else if ult can't hit multiples -- singed/udyr/vi)_
2. Amount of damage you did in a game
_(replaced with something else only if champ does not do damage -- soraka/braum)_
3. Amount of kills/takedowns you got in a game
... That's it. Nearly every single champ has the same 3 (with few exceptions where the same ones wouldn't work), and all they do is track stats.. on things you would do naturally in every game anyway, rather than specific things you need to actually try for.
All 3 stat trackings for a low low price 850 RP per champion.
Also, they are all labeled as "Set 1", so expect another round of "stat trackers" for an extra 850rp per champ in the future.
**Edited post for clarity**