Yes you do not need additional credit to build your scores.
If you follow advice on rebuilder board on how to use your credit cards you will improve your credit over time.
If you are trying to build up your scores for a purchase of a mortgage you would qualify for a mortgage now with a 660 mid score, depending on your other qualifications, income, employment, DTI, etc etc.
Good Luck
May all your dreams and wishes become a reality!