Blocking Reddit

Hi, I literally found out about Pi-Hole about 2 hours ago. However, I did read a fair amount of topics but either I didn't find an answer or maybe there simply was no answer to the question I'm about to ask:

Question: Can I block the entire reddit domain except for certain subreddits (and therefore their discussions (threads? i actually don't know how to call those things...))? If yes, do I have to add the exceptions as wildcards? Also, can I do it the opposite and instead simply blacklist certain subreddits?
Question over.

I apologize if this is too simple, but I can't start using Pi-hole for the next 2-3 weeks (I'm in the middle of final exams period and my raspberries are at my parent's place).
I'm mostly looking for stuff to block distractions and adult content since I intend to give up Windows (I honestly can't take it anymore) and fully migrate to Ubuntu (except that I need some CAD softwares because of uni so I'll still be running Windows in dual boot, but I'm talking too much, sorry) and in my extensive research (not really that extensive) I have not found softwares or solutions that aren't extremely above my level of understanding. I think that sums up everything.
Thank you for any feedback.

I use on Firefox the LeechBlock addon to do that : https://addons.mozilla.org/en-US/firefox/addon/leechblock/

Here is the list I put in LeechBlock preference just after :
"Enter the domain names of the sites to block (one item per line)"
old.reddit.com/r/news/
old.reddit.com/r/todayilearned/
old.reddit.com/r/worldnews/
etc..

So I can read most of reddit but not anymore these endless time sucking subreddit..