Cards that must target multiple creatures are not all that common in magic the gathering and yet when you do see them they can be very impressive looking. Perhaps the most obvious of these was hex, a card that can out a few years ago that costs two black and four colorless and allowed you to destroy six target creatures. This seems like a fantastic card, until you realize that it can only be played if there are six separate creatures to target and at this point you begin to realize that it might not be as useful as you think, and the first time you are being destroyed by your opponent because there are only five creatures on the board you see the flaw in the card.
This becomes less problematic with cards with less targets but the problem still exists. And Incremental Growth has this problem. An uncommon green sorcery from the Lorwyn expansion set of magic the gathering it reads "Put a +1/+1 counter on target creature, two +1/+1 counters on another target creature, and three +1/+1 counters on a third target creature." while it costs two green and three colorless.
The first thing of note is that six +1/+1 counters for five mana is not an extra ordinarily good price. It is not unreasonable but there are many good green creatures that are 6/6 for the same or very little more mana, and in the end the creature is better in many ways.
Cost aside though the real problem with this is that it insists on three different targets. And if you have three creatures out this is no problem at all, but against a deck with a high amount of removal that can become a problem. At the point where you have two mid range creatures out and want to increase them you have two possibilities. If your opponent has a creature you could give it a +1/+1 counter while giving five to your own creatures. This is a 4 counter gain, and it may be worth it, but again I point out the advantage of simply having a 6/6 creature.
The second possibility is that your opponent does not have a creature out. At this point this card becomes a blank. A card that is unplayable and therefor as if you had drawn nothing. This is the worst thing that a magic the gathering card can become since it is giving near automatic card advantage to your opponent.
In the end this is a fun casual game card, but nothing more.