Of course, accessories really "make" the outfit, in the 21st century as well as the 19th. Many Victorians thought that some kind of coat, shawl or other garment was necessary to lend the proper "finish" to a woman's clothes when outside, even in the warmest of weather! While period photos show us that not every woman wore a jacket, cloak, or coat every minute she was outside, your costume should also include outerwear like a cape or shawl. If you can find a ready-made cape that reaches to your elbows at least, and to the hem of your dress at most, that will work; check thrift stores at Halloween time. Your cape should reach all the way around your body, not just hang down your back, and it should be made of a dark fabric that looks like wool.
Dark-colored gloves are a also good thing to have. Avoid the polyester or crocheted lace fingerless gloves (or "mitts"), because they were really only worn inside the house, not on the streets during the winter in the 1850s and 1860s. Thrift stores, Wal-Mart and Target carry plain black and brown leather or leather-look gloves that are perfect. You can also use plain black knit gloves, and cut off the fingertips if you want, but be aware that cut-off or ratty gloves are a “lower-class” look! Don’t wear cut-off gloves if you have a modern manicure with nail polish, or very long fingernails, however!
photo ca. 1870. Sense & Sensibility.
You can also make a pair of "muffatees", to keep your hands and wrists warm while keeping your fingers uncovered, by getting a pair of old knitted wool knee socks in black, brown or other solid dark color, and cutting off the feet. Pull the leg portions on your arms so that one end covers your hands up to the first knuckle and the base of your thumb, and the other end covers your wrist and forearm. Use a needle and thread to take a stitch or two in the end that covers your hand, between your thumb and first finger, to make the muffatee fit better, and use Fray-check on the cut edge so it doesn't ravel. Or turn the edge to the inside and sew or glue it down. You wear the muffatees instead of gloves, and they can be worn both inside and ouside, but they are not fashion accessories, they are practical!
Jewelry should be simple and sparse: a plain gold band wedding ring, small gold studs or drop earrings, and a round, oval, or rectangular brooch at your collar are fine, but keep modern wristwatches hidden and leave the rest of your jewelry at home! For carrying those modern things like wallet, keys, water bottle and camera, get a wicker basket with handle to carry over your arm, hide your stuff under a cloth napkin or flour-sack kitchen towel, and you are ready to be seen in the shops!
Kay Gnagey’s 19th Century Costume Research Center
Elizabeth Stewart Clark’s Sewing Academy