What is the best teeth whitener?

I had an impacted baby tooth that I had removed a couple of years ago. I’m 21 so, obviously, all of my permanent teeth have grown in already. Because of this, the new tooth grew in crooked (a bit higher than the others). I’m not sure of the reason, but now this tooth is quite a bit duller than the others. It’s not yellow or rotten, but it’s definitely a different color than my other teeth and it’s embarrassing. I just noticed it today.

I’m looking for a teeth whitener with a brush applicator, but I don’t want to fork out a bunch of money if it’s not going to work. I want to apply the whitener just to this tooth until it matches the others, and then apply it to all of them once they’re even. I’m looking to spend $20—$25 at a drug store.