Good teeth whitener that wont break the bank.?

I am looking for a product that will whiten my teeth allot. Ill admit that i used to not brush them regularly so they are kind of stained and i want something that will help whiten them. I don't want to spend a lot of money every product I see is super expensive. any suggestions on what works the best that isn't so much? and I suppose if it is a lot and it works really well it would be worth the investment! thanks.