I dunno what country you’re in, but in my country you are required by law to have a valid reason to reject a job candidate. That reason can be pretty simple, such as “your application was not as strong as other candidates” but you need to be able to back that claim up if you’re challenged (and you can be challenged on it).

The recommended approach is to have a list of selection criteria, and carefully consider each one then write it down and keep a record of the decision for a while, incase you end up on the wrong end of a discrimination lawsuit. Candidates have the right to ask why they were unsuccessful (and they should ask - to find out what they can do better to improve their chances next time. As a hiring manager I would note down anyone who asks and consider offering them a job in the future, bypassing the normal recruitment process).

If your selection criteria includes “they need to wear nice clothes” then you’re treading on very dangerous territory and could easily be charged. The damages is commonly six months pay at the salary of the position they applied for, and can also include a court order for you not to be involved in the hiring process going forward.