If you can pass the exams with self-study, a masters is not necessary or really very useful. My understanding is that most programs only teach to the preliminary exams, so after you graduate you'd still have the toughest parts ahead of you. You could even argue that someone who has an MS in Actuarial Science hasn't demonstrated the ability to pass exams on their own, because they've been taught everything in a classroom.
I can only think of two ways a masters (in Actuarial Science) would really help you. First is if an HR person thought that made you a better candidate, but the final hiring decision is usually made by an actuary, and they'll give your MS almost no weight. Second is that the school might have career services which could connect you with companies for internships or jobs.
The traditional thought is that a masters (of any kind) is not at all useful for becoming an actuary, but if you really want one, consider Statistics, Computer Science, or Economics. Those would provide you with useful skills you wouldn't typically pick up on the job and could make you more marketable for e.g. predictive modeling roles.
