One of the easiest Halloween costumes you can put together is Katniss's outfit from the arena! You probably already have most of it in your closet, and if you don't, you can buy clothes you'll wear again.
Here's what you need:
A basic black tee. If you don't already have one in your closet, buying one isn't a big deal beacuse a good black tee is a wardrobe staple.
Military green pants. Katniss's are loose-fitting rather than skinny, so look for a similar pair in an earthy tone (browns and greens are both good). These are also pretty easy to find in clothing stores if you look a little bit.
Black combat-style boots. You can use any kind of short or medium boot for this. Just make sure they're black, brown or grey.
A black hooded jacket. Choose anything from a black hoodie sweatshirt to a leather jacket to a black raincoat - they'll all have a similar look.
Accessorize with things like a backpack and a bow and arrow. Don't forget to add the special mockingjay pin that Katniss wears (they sell them in a few stores, or you can make your own out of paper).
To finish off your look, do Katniss's signature braid. You can just do a regular side-braid, or check out this tutorial for instructions on how to copy her look:
Click on the gallery to see some Katniss-inspired outfits that would make perfect Halloween costumes!