The way to buy perfume isn't by what you sniff at the counter. A good perfume will match your natural scent and compliment it. Go to a perfumer and get as many paper testers as you can. Take them home.
Every evening try on a perfume, and never just after you bathe. It's best to bathe in the morning, don't wear any other perfume, and use unscented soaps and deodorants. Just rub the testers on your pulse points on your neck and crooks of your arms and wrists. Leave it on and don't judge a thing about the perfume for an hour. THEN solicit opinions.
Perfume is only half of an equation. Half of a perfume's real scent comes from your body chemistry and, like food ingredients, not all things compliment every other thing. Some perfumes, in fact many perfumes, which smell wonderful in the bottle, may not smell memorable on you. Your goal is to find those scents which compliment your own chemistry, rather than mask it, and make you truly more alluring. One of the reasons Chanel No. 5 is such a classic is that many men find it makes men think of sweating women with a slightly floral tone that makes them think of boudoirs and lace. Chanel No. 5 works well with the chemistry of many women and that's part of its success, but on some women it's overpowering even if used in small amounts. In others it takes on a slightly sickly smell.
If you have one near you, a real perfumer is something every woman should visit once. You go to them and they find scents which compliment your style and chemistry. You'll need a good day scent, possibly a sports scent, an evening scent, and a romantic evening scent. A good perfumer can match you with the right scents that men will notice and find appealing (if that's your goal) and complement your personal style. As you age, your body chemistry will change too and so your perfume needs will change. You may need a scent for when you're menstruating or pregnant as both of these physical states can change the way perfume interacts with your body. A good perfumer will help with that too.
Finding the right perfume is like buying a couture dress. It's a long and difficult process, there will be many fittings and adjustments, but when it's finally right, you will have a custom match which will make you stand out from all the other women.