Many genealogists start work on their DNA matches trying to figure out their “brick wall.” While that’s definitely a long-term goal, it may not be the best way to start.
If you are new to DNA analysis, it might be good to work on your matches for those families where you think “you know everything” already. It’s a great way to build up your skills and learn about DNA methodology. There will be “less to learn” since you already have the family worked up. And you will be better prepared for working on those “brick walls.”
You may also discover that you don’t know as much about the “already done” family as you thought you did.