Which stuff packs do you use most?

I have all the stuff packs, but Cool Kitchen, Movie Stuff and Laundry Day are the packs that I use the most in my game. I think it really depends on what you're looking for in TS4. Just try to review every pack on TS4 site and see what could be best for you.

I use "Kidsroom Stuff", "Vintage Glamour" and "Romantic Garden" the most.

Laundry Day, Vintage Glamour and Bowling Night

I only have 2 Stuff Packs, so I'm probably a terrible person to ask. But I really liked Romantic Garden more than I thought I would.

Originally, I just got it because it was part of a bundle, and it had some hair I liked. But now I'm finally using my households' backyards for something other than graves. Gardens really class the place up.

Laundry day has GREAT items. I also love Movie Stuff and Vintage Glamour (both also have really nice items). I don't tend to like the create a sim items in the stuff packs, but laundry day has some cute stuff for women. For them being on sale, totally worth it. I don't know if I would buy any other packs if they weren't on sale. These I would pay full price though.

I have all the stuff packs and use things from almost all of them literally all the time...really hard to say which I use the most.
In my sim's own homes, Laundry Day stuff probably wins that...but Backyard, Movie Hangout, Perfect Patio and and Toddler stuff have activities I utilize out in community lots pretty much every sim day and fitness stuff has those earbuds that I make very heavy use of (as well as some nice furniture that I like).

Even the stuff packs I didn't mention get heavy use. I think you can be happy no matter which ones you get, I know I would be if I didn't have any of them.

Cool Kitchen, Kidsroom stuff, Vintage Glamour,Movie Stuff and Laundry Day

If you're a CAS simmer, pick the one with the best CAS items. If you like building, pick the one with the best Build/Buy items (these are subjective so take a look at what you could get!).

I tend to use the Cool Kitchen, Laundry Day, and Movie Hangout the most, with the Fitness one coming in there too for CAS items.

Go to the store product page https://www.ea.com/games/the-sims/the-sims-4/pc/store
Click on each of the stuff packs and scroll to the bottom. There will be pics of the items in that pack.

I haven't played much with Laundry Day and Vintage Glamour yet (I just bought them last wk during this sale), but I know from looking at the items, they will get a lot of use in my game. I love the CAS and home decor in both. LD is definitely for my Sims that haven't "made it" yet and VG for when they move up (and for my Vamps). I see a lot of potential for LD as well if they give us Witches/Werewolves/Farming.
I actually enjoy family play in TS4 so Kids' Room and Toddler get a lot of use when I have families.
I love the ice cream and popcorn makers so I also like Cool Kitchen and Movie Hangout (MH has potential if I can get Gypsies in game - how I miss the Gypsy Matchmaker!).
Backyard has some nice outdoor items that don't take up much space (the bird feeder and wind chimes) and a fun object that is worth it if you have enough room on your lot.
Personally, I love Spooky. Ever since getting Seasons, I use this every Halloween. I love the pumpkin carving table. Yes, it's a "limited" use pack because you probably only make use of it during the Halloween holiday, but I couldn't imagine not having it when that time of year comes around for my Sims!