Suggestions for project management tool?

Hi, I have a small but growing web development business, and I'm wanting to find a good project management tool. Ideally I'd like to find a free or affordable web-based tool that can help manage projects, have a kanban board or to-do list, gantt charts, places for chat or discussion, and file sharing. Also, I'd need it where I can invite only select people to each project. For example, only me and developer A can see the chat, files, to-dos, etc, for project A, only developer B and me can see everything for project B, etc.

Any suggestions? Or other things to consider or features to look for?