Tsinaje Knight

Riverborn {w}{u} (When this creature enters the
battlefield, you may pay {w}{u}. If you do, put a
+1/+1 counter on it.

Vigilance

Whenever a +1/+1 counter is put on a creature you control, if it’s the first time counters have been put
on that creature this turn, put an additional +1/+1 counter on that creature.