If your goal is to get or maintain a good credit score, two to three credit card accounts, in addition to other types of credit, are generally recommended. This combination may help you improve your credit mix. Lenders and creditors like to see a wide variety of credit types on your credit report.
It's a good idea to pay off your credit card balance in full whenever you're able. Carrying a monthly credit card balance can cost you in interest and increase your credit utilization rate, which is one factor used to calculate your credit scores.