What is the best way to manage permissions

Question

What I have:

I am a site owner and have a site which will be shared by members of different subteams. The main page contins links to libraries, and in them fiels of particular teams are stored.
Goal

I want to create a set of permissions that will make it possible to share only chosen libraries, folder or files based on the group a person is in.
Example:
A team works on a project for HR. I want the team to be able to access all their files conntected to it and members of HR to be able to see just certain, chosen files.
I want to find the best practice for such a problem

Approaches so far
I created different permission groups
I am storing files of particular teams in libraries
I was thinking about creating a separate subsite for sharing with hr with links to files/folders and giving the hr permission group access to that subsite and just the particular, linked folders/files
I want to make the permissions as simple and easy to maintain as possible

Answer 1

Ideally, you wouldn't do this. Instead, you'd create separate SharePoint sites for each function. This way you can add people to the default Members group (if using a classic or on-prem SharePoint) or the Office 365 Group as a Member (if using a Modern Team site in SharePoint Online).

Not only does this simplify permissions management, but it leads to less potential mistakes.

If you can't do the above for some reason, create a SharePoint Group for each function and at the Document Library level (again would recommend one per function) break inheritance, removing groups you do not want to have access and adding the group you do want to have access. Remember to give your Groups at least View access at the site permission level if you want them to be able to navigate to the home page.