I just discovered this thread, so here goes...
I started playing The Sims 4 a little over a year ago. My first couple households didn't last long. I didn't know how to have adult Sims take care of themselves, let alone how to have parent Sims take care of their children.
Then I started the "New in Town" scenario, which taught me the ropes. After getting one of the endings (I honestly forget which one), I started having the character Farrah Nouvel explore almost every aspiration and career the base game has. Then she got married and started having children. My current game has eight households that I play in rotation: Farrah's household plus the households of seven of her children.
My favourite Sims 4 world is probably Oasis Springs. Farrah's household still lives in the Agave Abode lot that she first moved to at the beginning of the scenario, and most of her children's households are somewhere in Oasis Springs. Plus, the landscape and the architecture remind me a lot of the coastal California area where I lived for most of my life.
I only have a few packs (Vintage Glamour, Seasons, Growing Together, City Living, and the free Holiday Celebration), and I'm still exploring them, so it's hard to choose a favorite. But maybe Growing Together for the extra depth it gives to raising children (especially infants, who start out almost like newborns and then progress slowly towards toddlerhood).
I've done some building and I've created/managed households, and I enjoy them. But mostly, I enjoy playing the game and watching my Sims' lives unfold. Right now, my households include 15 adults or young adults, 6 teens, and 15 other minors (children and younger).