If you want to avoid interest and finance charges on credit cards always use only the amount of money that you can pay back in full.
When you purchase something with the credit card pay the full amount back each month when the bill arrives because by doing this you'll avoid any interest and finance charges on your credit card.
When you only pay half the amount owed or the minimum payment you're paying more in interest charges overtime so it's always better for both your finances and your credit score to pay more than the minimum credit card payment or pay the credit card balance off in full each month if possible.