Using a Credit Card to Improve Credit and for Savings?

Greetings PF,

In order to improve my credit and to have some extra money for my savings, I was thinking of getting a credit card that has a cash back incentive. I will be using it like my debit card where I would use that credit card, then pay off the balance immediately. I read that some cards have starting or yearly fees (or both), and/or some will change which things you can get cash back. I would just like a cash back credit card in which I can save cash on everything and have no (or low) annual fee. Which card would be best that fits the aforementioned description?

Also, somewhat related, I read from a previous post that Magnify Money was the best site to find a credit card. Is that assumption still true?

Thank you for your time.