General:
* Beginner
* Novice
* Newbie
* Fresh face
* Newcomer
* Unskilled
* Inexperienced
* Uninitiated
More formal:
* Neophyte
* Tyro
* Apprentice
Specific situations:
* For a first-time traveler: Tourist, sightseer
* For a first-time parent: New parent
* For a first-time driver: Learner, learner driver
* For a first-time voter: New voter
The best synonym will depend on the specific context and the tone you want to convey. For example, "newbie" is a more informal and playful term, while "neophyte" is more formal and suggests a serious learning experience.