@gbaisden do you just play with one family? I switch to a new one every few days. But sometimes I add relatives in CAS and make them into my next household, I like them to have extended families.
With teen Sims I often age them up and move them on to University if you have that pack. I don't like the dorm life as it really slows gameplay, so I make one of the lots a private residence for them. I haven't sent a Spellcaster to Uni though as I don't have any teen Spellcasters. Or I start a new Household for them and add a partner and create in laws to add to another new household and expand the family.
My Spellcasters are very different. I have Pandora (attached image) who chose to become a Spellcaster and is the queen of the duels. She's extremely confident and fearless and I created her as the most feared character in Glimmerbrook. Although she isn't evil, she's more likely to use dark magic. She's very defensive as she had to earn the right to be a Spellcaster. The most powerful Spellcaster though, is Aurora. She was created as a Spellcaster but she won't duel, she never uses dark magic and she's a Wiccan. Her home is full of the cottage living wild animals and I'm adding a unicorn character using Horse Ranch soon. She's all about the natural world and is very quiet, choosing animals over people.
Hiding away incognito in Glimmerbrook is also my mortal paranormal investigator, Olivia. She's a thrill seeking daredevil and she's moved to Glimmerbrook to investigate all things otherworldly. She moved into the house, weird things started happening and then her fiancé died while mountain climbing. He started dancing in the snow and making snow angels in shorts until he froze to death (that may have been my fault, cough) then she met Guidry the ghost from the mysterious paintings in her new house and started battling the paranormal.
I'm also going to be adding a Spellcaster to Moonwood Mill at some point, I added Werewolves because Glimmerbrook is too small.
I put a fair bit of thought into my plotlines because it takes me a few days to build my lots so there's plenty of time to think about the characters. Plus I'm rebuilding my game and adding back Sims I lost after console technical problems. As I've added more packs since losing them, I can add them back with improvements.