If you've never tanned a hide before...good luck. It's a tough job. I would suggest you buy a tanning kit. Tandy Leather carry's a kit that will do one average deer hide...hair on or hair off.
You can buy a deer hide for about $20 on ****. I wouldn't consider using hair-on deer hide...it sheds badly..never stops it seems, but looks good while the hair lasts. Deer hide is a bit stretchy and will work out of shape in a couple of years. Deer or Glove tanned cow hide is the best for what you want to do...soft like deer hide but much thicker and tougher. You can make it look like "brain" tanned leather by wearing the 'flesh" side out (rough side)
Frankly, if I were going to make a plains quiver and money was the issue to buying leather. I'd just save my penny's until I got enough. Check out **** or Tandy leather on line. Or if you are set on using deer skin..no hair, I have sides I can sell you for $25 plus the shipping. I currently have about 30 deer hides. None with hair on, just sold all of those I had. These are southern deer hides, meaning they aren't very big, but big enough for a plains quiver. You'll need two if you want long fringe.
Deer/Glove or Chap leather tanned cow hide is more expensive, but in my opinion the better choice. You can find it listed here
http://www.tandyleatherfactory.com/en-usd/home/department/Leather/Chap-Leather/Chap-Leather.aspx Or Google Hide House. **** is also a good choice. I have other resources if you don't find what you want there.
Again, you can give a go at tanning your own leather, but it sure ain't an easy process. You can do the old timey way, with wood ashes, a #3 wash tube and plenty of time. You'll need a beam or log also.
PM me if you are interested.
Art
Cedar Ridge Leather Works