Buying shell casings for the first time really does not have to be a hassle. Sure, there are lots of places to buy them, both online and offline, but how does one sort through the muddle of being a first-time casing buyer? Where does one start? And what are you going to do with them once you get them?
Most people who buy shell casings are reloaders (or those who want to be one). The rest are people who sell the casings to the reloaders, and depending on the reloader, may or may not be such a good idea unless you just want a little pocket change for your efforts. Here is your first tip: talk to some local reloaders and see if you can drum up a little cash for getting them from a firing range for them. They might just appreciate a few less errands to run, and if the range has what the reloader needs, you will be doing the reloader a good favor.
If you have decided to buy shell casings online, there are many places that sell them. Second tip: look at more than price. Most places will sell casings that have been cleaned and deprimed, tumbled, shiny and ready to go, and some places will sell dirty brass to those who prefer to do their own cleaning. You will need your own equipment if you decide to buy the dirty brass and then clean and deprime the casings yourself, but it is a pretty easy job.
Thirdly, by now you must have decided what caliber casing you need for your intentions. After that decision has been made, you can look around for pricing. Pricing will depend on your own budget considerations, and your fourth tip is lot size. The lot size that you buy will largely depend on what you intend to do with them. Just selling them to a reloader? Then the lot size is simply going to depend on how many you think that you will be able to sell in the time frame that you want. Lot sizes can vary from around 100 to 5,000 casings (or more) so some due diligence is required. If you would like to learn reloading, try a smaller lot size. If it turns out to be something other than what you had hoped, you can always sell the casings and whatever equipment you have already bought.
Lastly, there are quite a few places where you can buy shell casings. In addition to the usual ammunition and brass shops out there, casings can also be found for sale at recyclers and even online at Etsy. Really.