Yayyyy I love your game idea for BG3 city! If you’re taking asks, I’d love to read your thoughts about Gale’s school, the one he went to as a child. Maybe that’s where it was discovered he was a prodigy?
Maybe I’ll join in and tag you, too!
I'm sorry it took me so long to answer. I wanted to make it a fic, but then I realised I can only make a headcanon. And there will also be a lot of self-insert (because my school years felt like hell, I was happy to enter my Uni).
A little bit of lore first. As we know, Gale attended the Blackstaff Academy in Waterdeep (he says about it in the Arcane Tower). According to the Forgotten Realms Wiki and other sources Blackstaff is both a school and a university. Only the magically talented students are accepted as apprentices there, and they are at first taught by senior students (probably at the age of university students) and only after a few years they start being taught by professors. So future sorcerers and wizards spend more years in the Blackstaff tower than people do in school IRL. It's like a boarding school and a university campus combined, you can spend up to a couple of decades there.
We also know that Elminster first met Gale when the latter was 8 years old. Maybe it was the age Gale was accepted as an apprentice at Blackstaff. He was young, upset with his own abilities and very talented as a mage. Children at school can be pretty much evil, when it comes to relationships between them. I can picture Gale as a shy, naive person at first. Other children made fun of him both because they all thought they were talented and because he was always "lost in thought". They needed to call him twice or thrice to respond to them. Of course it annoyed everyone and made him an outsider. Maybe he was desperate to have a friend and prove himself in this community, so that he stole the Blackstaff (the staff of the very first headmaster, Khelben Blackstaff himself) and opened a portal to Limbo. /the story with the portal is also from the Arcane Tower dialogue/
In my view he only came to be respected by his peers when he reached the age when apprentices started receiving tutelage from professors and teaching the younger students. That's where, I think, Gale got his experience as a teacher (in the Weave scene he tells the character "I know" if they mention that he is a good teacher). I have a headcanon that his best friend from Blackstaff was a lesbian dragonborn, but she got jealous when he became the Chosen of Mystra, and they parted ways. But that character is only in my head.
We also know that Gale had romantic partners before Mystra. In my opinion he was good-natured, funny and handsome in his late teens and early twenties, and that made him a desirable goal for romance. He most probably liked the attention which he had thrived for in his childhood, so he had a lot of trysts and affairs with fellow Blackstaff apprentices of his age (of all genders and sexes, of course). Yet these romances were not meaningful enough for him to remember them and affect his life. His first serious long term affair was with Mystra, but I think it started after he graduated from Blackstaff.
Even when he was the centre of attention, he was still the weird guy envied for his talents and despised for his vast knowledge. He did not make any bond with his peers (or that bonds were shattered later on), so he had no anchor in the material plane to stop him from pursuing the Goddess of Magic.
That's what I can say on the subject right now. It's very self-indulgent (apart from the "centre of romantic attention" part), because I generally project a lot of myself in Gale. Nevertheless I hope it is interesting to read.