I've wanted to do a proper Sif costume for going on three years and either never had the means or was too intimidated to get my hands really dirty. In 2013, I took the plunge.
Sif's red underdress hadn't been pictured without her armor at the time (and still hasn't), so I took some creative liberties with it. I patterned it out of 2 oz vegetable tanned leather, which I then cut, dyed, beat, and weathered. The dress has a silk duponi panel and a panel of chainmail with over 20,000 links.
Her armor was made out of a combination of worbla, wonderflex, and craft foam. There was a good deal of spackle, gesso, modge podge, and acrylic paint involved. :D Everything was given leather straps or hidden velcro closures for extra support.
The faux leather leggings were bought. The boots were bought cheap on eBay and modified to look like hers, though I ran out of time (and worbla!) before I could make the boot armor.
The wig is a black lace front, and the contacts are Freshlook colorblends in hazel. Lastly, I used a Ben Nye bruise wheel to rough up her face a little. All in all...I'm okay proud of how this turned out, for being my first armor endeavor. The dress is flattering, and if the armor isn't comfortable, well, it's armor.
I'd like to remake it next year, now that there are ample hi-res pics of the armor out and I have a better understanding of thermoplastics now. So much I want to do, so few moneys.