Steampunk is a counter culture that takes its inspiration from the Victorian era with a futuristic bent. Sort of what would life be like in a Jules Vern world where steam power had taken hold instead of gas and electricity. The fashion is Neo Victorian. Victorian hats, both men's and women's are popular, as well as lace up ladies' boots, parasols and other vintage altered clothing. Old brass goggles or early round lens googles for men and jewelry made with clock parts and gears are part of the style. Think old brass steam boilers and high wheeled bicycles, as well as Victorian inventor-mad scientist. To pull off the steampunk fashion, you need to know where to find gears for your jewelry.
Most of the brass gears used in steampunk fashion come from wristwatches, pocket watches and clocks of all sizes. Look for yard sale broken clocks that cost next to nothing. Thrift shops and second hand stores are a great source of cheap or broken and free alarm clocks and similar pieces. If it doesn't work and is free or cheap, you will feel fine tearing it apart for gears to make jewelry or buttons.
Buy lots of small gears from online auction or craft sites. These are sometimes sold as watch gears to repair watches, but may be sold for altered art supplies or specifically for steampunk fashion parts.
Buy broken watches, alarm clocks and clocks in bulk from a pawn shop, watch repairman or antique shop. Cultivate a relationship with the owners of these stores so they will call you when they have busted inventory.