Grumgully, the Generous

Each other non-Human creature you control enters with an additional +1/+1 counter on it.

Goblin Anarchomancer

Each spell you cast that's red or green costs {1} less to cast.

Sol Ring

Thundering Raiju

Haste
Whenever Thundering Raiju attacks, put a +1/+1 counter on target creature you control. Then Thundering Raiju deals X damage to each opponent, where X is the number of modified creatures you control other than Thundering Raiju. (Equipment, Auras you control, and counters are modifications.)

Evolution Sage

Landfall — Whenever a land you control enters, proliferate. (Choose any number of permanents and/or players, then give each another counter of each kind already there.)