I'm a student at the last year, trying to find a software developer job, being as a junior developer, how many reputations are reasonable for getting a junior developer job, or if you were the employer, how many reputations do you expect the applicant have so that you have a strong feeling that she/he is the ideal candidate?
Reputation isn't about getting a job, it's about getting an interview, and it's only one signal of many. More concretely, it might be the thing that gets you selected for an interview over someone with the same resume but no stack overflow reputation, but it won't guarantee you a job anywhere.
The reputation is just a gaming mechanism to get you to share your knowledge as a public artifact on the internet. You should use those public artifacts as a way to help you land the interview and not overly focus on the reputation on your resume.