If cobbling (hand making leather shoes) seems like a complicated business, consider that historic reenactors, theatre costumers and Native Americans have all mastered the craft. Most historic shoes, like the moccasin, the Spartan sandal or the Medieval turn shoe (which looked like a ballet slipper) were very simple in design. Only the wealthy had an embellished shoe with elaborate embroidery and curled toes. Leather is, of course, an expensive material, but if you plan carefully, you can keep your expense down.
Most shoe patterns that you'll find are a variation of the moccasin or the Medieval turn shoe (which was itself a kind of moccasin). Moccasins themselves vary by design, and thus, the amount of leather you require.
Usually, the design begins with a tracing of the sole, adding an inch on all sides. The uppers are usually some multiple of the sole measurement. Thus, if you are a man with an 11-inch shoe, you can expect to use about 1 square foot of leather for the soles alone.
You can expect to use one and a half to two times that leather creating the uppers; thus, you should count on 3 square feet--nominally--to make a simple pair of costume shoes. Four is more likely. If you make a leather boot, like a Renaissance-era boot or Plains moccasin (which covers the calf), you can expect to double your square footage overall, for 8 to 10 square feet, or about a yard.
Every pattern will describe its requirements, which will determine how you purchase leather. For simple one- and two-piece shoes, the pattern may call for a single piece that is four times broader than the foot. Thus, you must purchase leather in a size that accommodates the shape.
Leather craft retailers supply patterns and materials for moccasins and simple shoes. Historic costumers similarly sell patterns, for everything from Roman sandals to 60s-era go-go boots. Christine Lewis-Clark's seminal book "The Make-It Yourself Shoe Book" is the most definitive tome on the subject (albeit dated, to 1979). Still, the simple patterns are perfectly useful today. Foxfire, the journal of simple living from the 1960s and 1970s, also published some simple shoe patterns, and is available in libraries.
You purchase leather by the square foot, not by the yard, which is how you measure fabric. A square yard is 9 square feet. Most leather is available as full hides, sides (which are half a hide), bends and shoulders, which are cut in squarish shapes of about 14 square feet.
One side or bend should be plenty to make a single pair of shoes, and even a smaller second pair. The leather you purchase should be a fairly heavy deerskin for moccasins, or a 6- to 7-oz. smooth leather. You may wish to purchase "splits," which are a less expensive grade than top-grain cowhide. Splits may have a sueded finish and better represent the quality of the leather that most peasants would have worn.
Because of your investment in time and effort, you may wish to have a cobbler attach a rubber sole to your shoes; this should be fairly minimal in cost (under $30, by the estimate of one local cobbler in 2010) and will add years of life to your investment.