IRL pioneer women didn't wear much jewelry because of the lives they lead. Slopping pigs, herding cows, planting gardens, tending fires, making bread, scrubbing floors, harvesting crops and other assorted farmwork just aren't suited for it.
Now in their finest get-up, depending on period - I'm guessing you want late Victorian if you're doing Laura Ingalls Wilder, some fairly ornate earrings would be all right, along with a brooch or a necklace, even a bracelet. Victorians loved ornate things, remember.
However, if you're wearing a prairie dress with a sun bonnet or a poke bonnet and it's all very rustic? Hmmm. I'd do it up like it was some poor pioneer woman's Sunday best - iron everything, be very careful - and then add one small piece of jewelry, probably a brooch, maybe some little earrings.
Okay, I did a google on Victorian pioneer jewelry. This looks like what I was thinking of.
http://www.recollections.biz/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=R&Category_Code=Jewelry
(Note: Fashion in the latter part of the 19th century is NOT my strong suite. When asked to dress in that period, I invariably go for a Storyville girl, just because I know that with frilly drawers, chemise, a couple of really frilly petticoats, the right boots and a good corset I can get away with it and be period, if not socially, appropriate.)