(Note: I think this would be the right forum to post this in, if there's a better place for it...feel free to move it!)
So, I've been restocking a lot here lately and I'm trying to stock with things I think people are more likely to be looking for. I tend to catch myself looking for wearables more often than other things, but I didn't know what other users look for the most. Food? Stickers? Beanbags?
Book Nook is competitive, but a good bet usually :)
You might also want to try restocking at Apocalyptic Apothecary and Magic Box. It's also quite competetive like Book Nook as stated, but the stuff you may get (Boosters and Potions) sell extremely well, especially Boosters. :) That are also the shops I'm browsing the most. Sometimes I stalk the food shops but not as regularly as the ones already stated.

Thanks you guys! I've been trying to do more books this weekend with the library quests being featured.
If you don't get much luck there at first don't be discouraged! It takes time to learn which books are rare and there'll be a lot of people there this weekend. Keep trying :)
You can also check on Seedlings every now and then, there isn't a LOT of profitable stuff there, but there's a chance of grabbing an Ornate Pitcher or an Aenoid Seed just sitting there, since not a lot of people rs there often!
I usually check the shops and just keep an eye out for anything that looks different than whats normally there. Sometimes it just turns out to be a normal rarity item that I somehow never noticed. Considering the user shop prices for normal rarity items seem to be increasing there's a chance you could make a good chunk of profit.
I agree! I've been really trying to look for different items that I don't spot in every shop.
I guess I need to start browsing the main shops in my spare time, lol. I usually am so busy doing other stuff when I'm here. I don't like to buy anything from a main shop until I check the price that users are selling it for. Sometimes an item that's RSing in the main shop for 2000 or more is being sold by tons of users for 300 or some other ridiculously low price!
I learned how to restock from the Food Market, and I usually restock there. Sometimes, the Book Nook too. I also sell the Shinwa items that I get, as the stat boosters can earn you a great profit since you paid 0 for them.
I often hit Ctrl/Command+F to look for items with only 1 in stock when the shop is pretty much full. This indicates to me that it might of value. I then search it up in the Shop Search to make sure that I'll make a profit. This method works for me because I hardly restock at stores that are more competitive.
❄️ Seeking Elsa or Olaf inspired CWs ❄️
I tend to stalk the plushie shop in my free time. I used to do so only for myself, but now that my collection has gotten decently large, I've been buying things to resell as well :) I'm pretty good at knowing what is valuable now, so I might move onto another shop now that I have that one down. Not sure yet xD I am comfortable there!