Oooh i see, I hope everything goes well! Although if your brother is already using they/them pronouns he seems to at least be aware of how to be a decent human being, I'm sure your parents won't be too far off! In any case you can always rant on here as well, no one gets judged!
It's basically just an additional collecting game besides badges/awards. Which you can get here as on most other forums as well, as for the Card collecting & trading, there should hopefully be like a 101 guide of it which hopefully helps make more sense of it, but in short
You have a daily task of 3 threads + 20 posts a day, if you've done that you can simply just request a card
here, and that's basically it