Urban Outfitters Silence & Noise Red Space Dye Dress
The red version is rare, but the gray version is pretty common and many people have successfully dyed it to match the red version almost perfectly. They gray versions come up on eBay quite often. It is also quite stretchy, I'm usually a small but have tried it on in XS, S, and M, and it was possible for me to wear all three reasonably comfortably. I have to say, off all of Clara's dresses, this is by far my favorite just to wear. It is so comfy, and flattering, and was actually warm enough to wear all this last winter.
This dress is probably her easiest to find SA dress, but that is for a reason: it is notoriously ill-fitting. The fabric is extremely flimsy and the fit is way too tight. This causes it to pull around the buttons and gap. Added to that, the buttons fit loosely in their holes, and the pulling causes them to pop out. So basically, you breathe in, the whole front comes unbuttoned. The size problem goes further than that. I normally fit a S, and I've tried on a S and L. The S was basically what I just described above, but when I wore the L, which was two sizes up from normal, it still was too tight in parts and gaped at the base of the bodice, though it was clearly too loose in the bust. Here's how I fixed it. I sewed a zipper in behind the buttons. Works perfectly. I can even wear the small now, though it still fits tight. I just zip it and button it up over top.
Worn in: The Rings of Akhetan
Urban Outfitters Pins & Needles Ditsy Dress
This dress gathers up in the back with a laced section, so it is an easier dress on the sizing. The only thing is that it is shorter than most of Clara's dresses, and tall people usually want to size up to accommodate this.
Worn in: Hide
Urban Outfitters Vaudeville & Burlesque Ruby Short Sleeve Fit & Flare Dress
This dress does not come with a collar, the black collar was bought by the Doctor Who wardrobe department and attached with snaps. It buttons in the front, though the button is usually hid behind the dress. I honestly don't have a clue what the fabric is, other than that it is matte. The sleeves were shortened by about an inch for Clara, and possibly the skirt too. It isn't quite as tight fitting as it appears either. They might have brought it in at the ribcage for Jenna, but I won't swear by it. It also has pockets! Very useful for Cons, especially since she doesn't wear it with a jacket or purse.
Commission a replica here: https://www.etsy.com/listing/169435712/doctor-who-clara-cosplay-costume-journey?ref=shop_home_feat_1
Worn in: Journey to the Center of the TARDIS (outfit #1)
NW3 Hobbs Elm Tartan Dress
Elm is the name of the tartan; Hobbs has made other items in the exact same fabric. This dress is probably tied with the Journey dress for most sought after. Unlike a lot of Clara's dresses and skirts, this dress is tall girl friendly! It is actually much longer than it appears on Clara. I'm the same height as Jenna exactly, and the dress comes to the top of my knees. I counted the stripes in the tartan, and I think they shortened it by up to 5 inches for the episode. It also has pockets! Some people think the pockets are false, but that's just because they've been hand sewn shut at the top. I'm assuming this is to protect them until they reach their owner.
Worn in: The Name of the Doctor
If you are looking to make this dress yourself, I would recommend searching for Blackwatch Tartan or Blackwatch Plaid. It isn't perfect, but it is fairly easy to find, as tartans go. And you will find it in wool or an acrylic/rayon alternative that will look much more accurate than anything Spoonflower can print.
Jenna wore this dress for her first promotional photos as Clara. Not many people realize this until they receive the dress, but it is almost entirely backless, just fyi.
Worn in: First Promo Shoot
Yumi Technicolor Dress
I actually think this dress is prettier in real life than it appears. The pattern is actually really colorful and detailed and has streaks of gold. But the waist tightness runs a bit small on sizing.
Worn in: Doctor Who Bonus Minisode
River Island Bright Tea Dress
Just a note: this dress is very fragile and falls apart through improper care, and while it isn't too rare now, as time passes I think it will become so.
Worn in: The Day of the Doctor
Alice McCall Navy Sea Rose Dress with Cutwork
This dress was made by Alice McCall, an Australian designer. (That was a massive hint, hint.) (OK if you don't get it, check ebay.au. I've seen like three on the Australian eBay, and none on ebay.co.uk.) Also, the fit is weird. Or maybe I just have too short of a torso. At any rate, it's too loose in the shoulders, and very tight in the hips on me. They almost definitely altered it for Jenna, and the way it is sewn at the appliqué parts would have made that easier to do.
Worn in: Listen
LeLuxe Vamp Dress
This dress is sold in multiple colors; the one Clara wears is in either copper or gold. It is from LeLuxe Clothing Co., a luxury Hollywood designer that specializes in 20's inspired beaded dresses (spoilers?!). The same company also sells basic slips. Clara's black slip could either be from this company or one that is custom made to match this dress perfectly.