Clearly no matter how long you abstain from the purchase of cereal bits, you won't achieve the purchase of, say, a ring with diamonds that can be seen without a magnifying glass. What you can achieve, however, is a string of real pearls, not plastic. Or a real gold chain, by which I mean 14 Karat or 18 Karat. Accept no substitutes. If the chain is at least 18 inches long, you can add a pendant - or if you want to get cute, an antique charm.
If you collect two or three chains, of whatever length, you can wear them together - like the "layered necklaces" that are popping up all over the internet. Or you can string them one after the other, finally close them into one very large loop, and double the loop around your neck with a "shortener."
Here's a good starting place to look for components. If you don't keep a pair or two of needle-nosed pliers in your desk drawer, a local jeweler can attach things for you. Or you can order a length of chain and the clasp of your choice, which is more fun.
If you like a more antique look, I've found some fascinating things at Nalfie . Bear in mind that like any dealer in antiques, the stock can vary from day to day. Note that one or two antique watch chains make a nice necklace. Or bracelet.
When I buy estate (jeweler-speak for "used") pieces, I'm careful to check for the metal content and for any hallmarks. 18 carat and 14 carat content are usually stamped into a piece by the maker, in an inconspicuous place. Sometimes the maker's name will be shown as well. On the web, look for detailed pictures.
What about scarves? Well, the first time I traveled to France, I decided not to buy lots of little
Volumes have been written about the consistent value of a really fine scarf. You don't need that here. The ones that appreciate most in value are generally the ones you wouldn't part with anyway.