In your navigation profile you can select a default home page or even a role based homepage. The name is a bit misleading, you can also select a microflow here. You can place your desired logic in this microflow. Be sure to place a show page action at the end of that microflow so the user does really end up on a homepage.
Your $currentuser is a variable in this flow so you can retrieve any associated objects or use attributes of the user object here. If you need the account object instead, you should use the cast action in your microflow to get the account object instead.