I had a necklace (bottom left) that was a little long for most shirts so I added a jump ring. It can still be worn at it's original length too. I timed how long it took me to make one on the right and I was shocked it took a half hour to assemble and deal with the jump rings.
Children's blank Bracelets These just barely go on my wrist too. But they are 2.0 inches. The next size up seems to be 2.4 inches. Sometimes 2.6 inches is used for women. 2.2 would be better for me. I bought a bracelet once with charms on it and it was 3.0 inches and incredibly large. That's what made me decide to try to make my own jewelry.
Unicorn Necklaces (part of a kit) Now if you don't want to be making a ton of necklaces you can just buy some unicorn best friend necklaces. These have made great gifts in the past. We are on our second batch of these. Unicorns are apparently a big thing with the kids.
Thin necklace chain It comes out to less than 40 cents a necklace! It is too thin for some of the jump rings and some jump rings are too little to go around charms. So I also ordered the 2.0 mm chain instead of just the 1.5 mm chain. It comes with 20 clasps and 30 jump rings. I'd say at a minimum you need 40 jump rings with 20 clasps. At 18" a necklace you'd get 24 necklaces. Most kid necklaces are shorter than 16" so you'd end up needing more clasps too. But you definitely need more jump rings that fit. Some necklaces I was splitting with the infinity symbols so 1 necklace uses 4 jump rings.
Jump Rings (since I ordered, I saw this one with tools) None of these jump rings will fit through the chain of the 1.5 mm chain but they fit around it. They are just a little too thick to go into it.
You will also need needle nose pliers and wire cutters but I already owned both.
Keep in mind how inexpensive the chain is and the clasps and the jump rings but then you have 100 charms or 36 feet of chain so then you have a lot of supplies. It's not worth it for a couple necklaces/bracelets. We will be making these for gifts and for ourselves. But we will probably have a ton of charms leftover but then want different charms too. I'm still trying to look into some form of nylon for bracelets with string but I haven't done ample research yet.
I still need to figure out nylon for bracelets to use some of the infinity symbols and then make them adjustable. Have you ever made any jewelry yourself? I used to make jewelry all the time with beads growing up. But I never had charms.
Links are affiliate. Trying something new since people buy stuff after I spend all the research figuring it out.