Length Knowing the length needed is a necessity. Nothing is more bothersome than noticing your clothes or your jewelry are too tight. It is equally annoying when a bracelet is too loose. Know what you need.
Design Buying a bracelet with 200 gemstones in it seems easy enough, but try to notice how the gemstones are set. There are usually 4 prongs for every gemstone, so you might potentially end up with 800 little clothing snaggers. Comfort and "wearability" are key.
Strength Buying an 18K bracelet will only raise your chances of problems down the road. 18K is softer than 14K gold and 14K gold is softer than 10K gold, so prongs holding gemstones bend more easily, increasing the risk of lost stones with higher karat gold.