Cloaks come in several varieties.
- full circle cloaks
- three-quarter circle cloaks
- Mantles or half circle cloaks
- brats or rectangular cloaks
They keep the rain off and provide some protection form the cold. A good woollen cloak, even without waterproofing, can take a long time to soak through, and can be easily discarded when you go indoors. However an extra undertunic (thermals suffice until you can make enough) is often warmer, as cloaks blow open. Some tabards and surcoats (especially fur-lined ones) are also good garments to wear for warmth.
Cloaks can also be used as picnic blankets, bedrolls and full circle cloaks can be large enough to shelter a friend too.
Cloaks generally take a lot of fabric. Although other fabrics work, wool is a great fabric, and a cheap source of large lengths of pure wool is op-shops/thrift stores/charity stores where blankets sell for generally about half the price of the cheapest wools, and can sometimes even be found in matched pairs for the larger cloak.
Remember that many cloaks were worn to keep the wearer warm and dry. Furs are warmest as a lining, rather than on the outside (although in some cases fur on the outside might be symbolic). Velvet wasn't invented till middle period, and was an expensive fabric mainly used for court garments and furnishings, and shiny crushed velveteen synthetic fabric will mark you as a newcomer (but if you are, you'll be nice and warm still).
Cloaks range from very simple to make to moderately hard. Some early period "rectangular cloaks" are basically draped blankets and can be made with no sewing. Also poncho-like cloaks, requiring little sewing, were worn, chiefly by women at this time.