Take a look at this game of MLP CCG.
What went wrong? When was this game lost?
This game was lost when you constructed your problem deck.
On 7 action tokens, you should be able to hit your problem that requires 7 power total. You aren't running any inefficient friends, so you get power equal to the actions spent on them. In fact you're even one AT ahead of par by moving Pinkie Pie to get 2:3 cost:power.
But you can't do it, because your characters are the wrong size for this problem. You are running a problem with 4 pink requirement but no characters of 4 pink power! Likewise, that 3 non-pink requirement does not match the 2-power Blue Moons in your hand.
Because of the mismatch between the size of your problem and size of your characters, you put yourself in a situation of needing to overkill your problem with extra characters. To confront My Pinkie Sense Is Tingling, you are going to need to play or move all four of these characters to the problem, costing 9 AT total. This is not inefficient on power deployment: you still get 10 power deployed for the 9 actions. But what you can't do correctly is deploy 4 and 3 of the colors you need.
"Oops, I don't have enough pink for that problem." If you've played enough games of MLP, that has surely happened to you. You probably blamed it on a stroke of bad luck and the heart of the cards not going your way that day. But no. It happened with mathematical predictability as a consequence of what went into your deck. Let's fix it.
The answer to "what problems should go in my deck?" is very often whichever problems in your colors have requirements that match the power of the characters you are using.
As another example, here's a favorite pair of buddies from a Taxes white/purple control deck, Rarity mane with Twilight Sparkle Ursa Vanquisher. Fashionable white players are always tempted to go with the white problems that do interesting things like Fashion Feast which puts cards in the discard for later reuse.
But notice the hidden cost here. The 4 requirement on Fashion Feast will require paying for an additional white character along with Rarity, a cost that will likely subsume any advantage gained from the problem's effect. Rather, use Monitor Everything that these two characters can solve all by themselves for no additional cost. This makes a difference and you will win more games with problems correctly tailored to your characters' measurements.
In particular, be very careful about any problem with a requirement of 4 in a color. No mane character does that by herself. Some colors (white, pink, yellow) don't even have a single 4-power friend outside of the overcosted Elements and ultra-rares! Blue and orange can do 4-power problems just fine thanks to Holly Dash, Full Steam, and Big Mac (either one). But be very careful about putting problems like Pinkie Sense or Fashion Feast in your decks of those colors.
This concept can be taken to a far extreme: design a deck with nearly every one of the problems and characters sized in lockstep. In fact, this is the genius of the "Ballroom Blitz" yellow/white aggro deck that has dominated the first couple Regionals tournaments of Canterlot Nights.
Notice the fantastic consistency in how the problem requirements match the friends. Just any single one of the white friends is enough to solve the white half of any problem. Most yellow characters can solve the yellow half of most problems, or at least the deck is flush with 1-cost critters to shim any gap. This consistency lends the deck enormous reliability in grinding through a long tournament, immune to any difficulties about being just one power short of a color requirement.
We really don't care about what any of the problems actually do. The correct fit is more important and matters more towards winning games. Even Best Pet really just improves its own fit by fetching the free Forest Owl.
This concept of matching numbers can extend further than problems. The colored requirements of your maindeck cards matter too, such as how Stand Still also precisely matches all of the white entry friends in Ballroom Blitz. More on this topic another time.
Now go forth and deliver some precisely tuned problem decks along with your favorite colors and ponies. Have fun!