The most common size used by Scout patrols is the 12" wide, 6 quart camp dutch oven. I think most DO recipes target the 12" 6-quart DO.

I'll also recommend Lodge cast iron. Just don't make the mistake of getting their dutch oven that does NOT have the legs on the bottom and the rim around the edge of the lid. Those "other" kind of dutch ovens are made for indoor oven use - rather than outdoor camp use. Lodge calls the the outdoor use versions "Camp Dutch Ovens".

BTW, if you've never tried a Lodge cast iron fry pan (Lodge calls them skillets), please do so. They are wonderful. My favorite is the 12", though for the amazingly low price you can get the 10.25" and the 12" and they nest together nicely (w/ paper towel in between to protect the sweet finish).

I've read several reviews that rate a seasoned cast iron skillet as being better than the very best of the fancy non-stick cookware.