There isn’t necessarily one “ideal” for all programs and all institutions. This will vary. It is to someone’s advantage to be involved in professional organizations or other extracurricular activities, particularly when a leadership role has been held. Internship and full-time experience is important to many business programs. Some programs require full-time work experience, while others, strongly prefer full-time work experience.
Internships are definitely expected and will benefit you whether you go into the job market right away or go to graduate school, as long as the experience is relevant; relevancy is key. Holding leadership positions in organizations demonstrates your leadership potential, which is important in business school.