Where to buy clothes?

Outfits:
This is something I am still learning, however many queens have had luck getting them from second hand stores (adding extra's to it as well such as buttons, sequins, rhinestones) or buying them from sites like ebay. If you want to buy them new and have the money, check out Sequin Queen. They have an assortment of fabulous attire.
If you are going for a certain look however, say a pirate for some reason, then check out costume shops. You can get costumes that already come with accessories and other goodies. This is probably the cheapest way to start out drag.

Shoes:
If you have a female size foot, usually you can find shoes up to size 11 in women's up to a 9 at most mall stores, then you can probably find shoes pretty easy. If you have bigger feet, you may need to find someone to special order them from. Here in Phoenix, Arizona we have a place called Boom Boom LaRue's. It is a clothing store that caters to the community. You may want to ask local queens what is available in your area.

Jewelry:
When starting drag, big bold jewelry isn't necessary. However, you should expect that either later down the line, or if you chose to do pageants, people will expect a queen to have queen like jewelry. This kind of costume jewelry can tend to be expensive and a lot of newer drag queens borrow these from their drag mothers or friends if they can.
If you are interested at looking for costume jewelry a local queen here runs a website called Made for a Queen. They supply an assortment of costume jewelry, along with some drag queen tips, and other things such as makeup.
If you are interested in a smaller form of jewelry walk around the mall. Many stores will have sales and offer beautiful jewelry at awesome discounts. One of my personal favorites is called Tinker Bella. They have sparkly jewelry, I love that!