If you're looking for a more natural, cheap alternative to cosmetic bronzers, just look in your kitchen cabinet and see if you have any unsweetened cocoa powder. If you're in the habit of using bronzer, cocoa powder works as an amazing alternative. The deep, chocolate color of cocoa powder also works fantastically well for contouring purposes. It is important to only use unsweetened cocoa powder, to avoid sweeping sugar or other sweeteners onto your face.
Just set aside some cocoa powder in a small container, so you don't contaminate your entire box of powder, and apply it to your face using a contouring or bronzing blush as you would regular makeup. Cocoa powder is a pretty dark powder though, so remember to tap off the excess. If it's still too dark for your liking, just mix some corn starch into it until it's a shade that you think is appropriate for your skin tone. This is pretty much the same idea as using corn starch as a face powder, just with different ratios.
If you're allergic to cocoa, I wouldn't recommend using cocoa powder on your skin. However, if you have no sensitives to cocoa, I say go for it. I've been doing this for awhile and have not had any adverse reactions or breakouts due to using cocoa powder on my skin. Some people use cinnamon powder in their home-made bronzer recipes to create more of a glow. I would personally advise against this as cinnamon can be a very strong irritant, and there is a risk that leaving cinnamon on your skin for an extended period of time could cause irritation, or even a more serious rash. However, try it if you really must, just be careful.
In my opinion, cocoa powder seems to have much better staying power than many other pricey cosmetic brands of makeup out there, which is great, since it's much cheaper and one box lasts a very, very long time. Not to mention the fact that I usually have so much trouble finding affordable matte brown makeup colors for the purposes of contouring and bronzing. And even better yet, sometimes when I'm out and about, I catch the very slight scent of the cocoa powder on my face, and every time it's a subtle and pleasant sensory surprise.