Hi ming wu, When u start your career than i feel job agent is really required but if he is not taking commision from you. Try to give as much as interviews you can give cazzz if you do not perform in 5 interview than you will probably thru sixth one. After interview when u come back, try to solve each and every interview question which you are failed to answers while intervied. Hope you understand what i mean to say.
Also very important, Update your resume on good Job sites. Take time while updating your resume on the same. Job agents will automatically start contacting you.