Vannifar is a four-mana green and blue 3/4 that allows you to do this for free at the beginning of combat on your turn, or you can put a +1/+1 counter on each colourless creature you control
The other four-drops on our list, Talion and Trouble in Pairs, both have significant colored mana requirements in their costs
Not all of it is downwards, either, so lets get into it and see what opportunities exist right now, and which hint at future ones
To triple a creature's power, that creature gets +X/+Y, where X is twice that creature's power and Y is twice that creature's toughness when Tifa's Limit Break resolves
This Halo Foil can reach as high as $140, but the market price is around $120
An easy way to think about Active Player priority is that the Active Player has the right-of-way. In MTG, we refer to this prioritization as APNAP (Active Player, then Non-Active Player)