nacho where is it you get all the not Lego but actually Lego sets? My kid is now a Lego freak and they're damn spensive.
They all came from aliexpress. There are several different brands (Lepin being primary among them), but I can't tell the difference between any of them, never had any real duds. Most are 50-75% off the MSRP lego price. They aren't perfect, but for the price, you can tolerate a few minor niggles. Every once in a while they'll put in a handful of light gray bricks that should be dark gray, or some such nonsense, but it's beyond minor. A few of the older sets didn't have numbered bags, so you'd have to sort, but they've gotten better at that in the last year or so. And it usually takes 3-4 weeks to get them (during normal times). But again, if you're saving $300 off a $400 set, it's pretty easy to give them a little slack.
We've built probably 8-10 of the citiview series that are 2-5k pieces, and they're great. Son also built Death Star, Star Destroyer, Ewok Village, several of the 3-4k-piece ninjago city sets. They even have some nifty original designs like a 3-story Barnes & Noble, a big shopping mall, and a Dinosaur Museum. My favorite is a "little" 1500pc McDonalds restaurant. We probably have 75 thousand chyner legos in our house.
I have a couple of sets left in storage, and we're rationing them. The boy would build a 4k set in a single day and be asking for more. He's insatiable for bricks.