Excellent app strategy!! You will LOVE the Discover card! Use it often and pay a good bit more than the minimum payment each month, and they will take great care of you. Welcome to the family!
As far as keeping up with numerous cards/accounts, I've found the best way for me is to use an Excel spreadsheet. I track the monthly "due by" date, the minimum amount due, then the actual amount I pay and the date I make the payment. It helps tremendously! Good luck!!