Well this is the most complex outfit I have ever made, and I hope that my 5 1/2 yards of ultra suede doesn't have too many accidents. I got most of my starting information from:
http://www.alleycatscratch.com/lotr/Elf/Arwen/Chase/MakingChase.htm
So thanks a bunch! If you want to see the actual links of the real Riding Outfit, I suggest visiting her site. She has the best Info out there.

I was really excited when I went to Joannes fabric to find my gray suede,

and I looked everywhere and couldn't find anything I liked, but when I went to the back of the store in their upholstery section and remnants, I found a pile of bulk suede and under it all was my dark gray soft suede. It was also on sale for 4.00 a yard so I was dancing in the aisles. I found two kinds of dark Grayy/purple ribbon I liked so I got both, and plenty of gray cheap fabric for my muslin.
Now to dissect Simplicity 9891.

2.

I didn't have any tracing paper so I just used news paper. It wasn't so bad. Here you can see where I added about 2 inches to the seam. Eventually later I added more and rounded out the top of the extending neck line piece.

You can see more of the proper instructions at Cat's site on how to do this, she has great diagrams.
http://www.alleycatscratch.com/lotr/Elf/Arwen/Chase/AlterPat.htm

This is her figure one example.

3.

I added a little more to the neck line also to make the collar stand out more.

4.

I modified the Scalloped skirt:

5.

Then I cut the bodice pieces from the skirt pieces. It will be easier I think to sew the bodice first then the skirt. I used newspaper and some scrap white paper to extend the seams because I cut them too short. But that is what the muslin is for.

6.

Well here are the finished pieces for my muslin. I cut the back into two pieces by accident, and didn't put the yoke on, but it helped to see how much allowance I would need from the final pattern.

Many pins were used which made it quite hard to try on but it fit nicely.

7.

Here is how I fixed the back panel of the pattern.
I put together yoke number 16 with back panel 3, and made one large piece for the back. Otherwise you would have a very low back.

8.

I will probably give a few more inches on all pieces of the bodice to be safe. That will not be a problem. I eventually added the Yoke to the back piece pattern and made it one big backing so it would go up to the top of my neck. Duh, can you tell I don't do much about sewing.

9.

I like the front but I may extend a few more inches near the zipper.

10.

I put the arms on, I may need to shorten the top sleeve, and I may modify some more the bottom sleeve. I don't like how it comes to a point. So I need to round out the edges of the bottom sleeve.

11.

Here is the modified sleeve, I rounded the corners near my wrist, and sliced through the top seam to let my wrists show through the top more. I rounded the bottom fullness also. It is a bit different from the original sleeves, but they look cool, and I will probably try a few different types of sleeves.

12.

Here is the mock up of one side of my muslin. I am very pleased.

I am too giddy to make the other sleeve since they will be identical.

I will start cutting the skirt pieces soon.

I started cutting out my suede, and I started with tracing the pattern on the sleeves. I used Carbon paper, and printed out the right size pattern. I did one for each sleeve side. I got the tracing carbon paper from Staples, but I'm sure any fabric store, or office supply will have it. It was about $10.00

Here are the results, pretty nice I think. I used a silver and pearl fabric paint from Walmart called Polymark Dimensional Fabric paint. I mixed two colors together, White Pearl Iridescent and Silver Pearl Iridescent. It cost like $1.50 each. I used a tooth pick to blot on the paint. This took me a whole afternoon, but it was well worth it.

And Here are the Results up close.