Is an agent super necessary for booking acting jobs?

An agent doesn't charge the actor. They get 10% to 20% of what the actor makes.

There are tools you need to even be ready for an Agent. Agents only get paid if the Actor gets booked. You are years away from needing or getting an agent.

Most aspiring actors, even us professionals, find jobs ourselves. There are on-line services that post audition notices. The best are Actors Access and Casting Networks. Yes, they charge a reasonable yearly fee.

Before you are ready for those, though, you need: Training (school drama club, school plays, community theatre or acting classes in your area). Classes do cost money, usually; unless it's through your grade or high school.

Then, you can study theatre or film in college. You need professional photo(s) called "Headshots", a resume with your acting experiences.

So, early in your acting career or hobby, an agent is really the last thing to worry about. If you are under 18, your parent(s) or guardian would need to pay for those tools and get you from audition to audition.

Child actors are not expected to have huge resumes, at first; nevertheless, if you have some real talent and your parents are willing...ask them to get you some professional training in your community. If not, stick with your school plays and when you're 18, see what you can do.