Budget wisely. If you are not planning on collecting aggressively, if you are not going to jump into the deep end, then you might want to buy a piece that is a little more mainstream–the little black dress of estate jewelry, if you will. If you only have one or two pieces, and the budget doesn’t allow for more, then you might want to get something you will wear over and over again.
Do your homework. People don’t even go to the movies without reading the reviews. If you are new to acquisition, then every piece might look fresh and original to you. Be aware of how to make an informed choice before you start spending all your money. A little bit of homework on what is popular, what is trending, what is long lasting, what is perennial goes a long way, but it is equally important to know who you are buying from. Research the dealer’s background, their expertise, and how long they have been in business. A dealer might be making unfounded assertions about relative value and desirability because they don’t have a wide range of experience. Compare their assertions to what the market as a whole believes. If you are spending a significant amount of money, a portion of the price may be related to provenance–who the prior owner was, in addition to who designed it, the age of the piece, and the materials. If a dealer says a piece is made with natural pearls, a diamond of a particular quality, untreated gemstones or owned by a particular celebrity, you may want to ask for this in writing.
Don’t overthink it. All that being said, collecting should be an enjoyable experience. Don’t get lost analyzing every component part of a piece and forget about the overall look. How a piece looks and makes you feel is just as important.