Target also sells a standard duvet set for $30 with no frills that you can easily use this technique on.
I've used this technique on my duvets and accent pillows over the years and they have held up great! All you need are pillows and a duvet cover. If you want to go uber cheap, you can pick up 2 standard pillows for about $5 and make your duvet out of two sheets instead (tutorial here). You'll also want to have a ruler, fabric marker (not a sharpie as shown :) ), and a sewing machine. If you don't have a sewing machine, you can follow this technique (tutorial here).
Okay. First step. Turn your pillow/duvet inside out and measure. To get the diamond pintuck, do 3 on top and bottom and 2 in the middle for pillows. For duvets, just make sure the marks are offset. To do the square pintuck like on the white pillows in the above picture, do three rows of the same. I believe I did 5 tucks on each row.
And like this when a pillow is in it:
Here's a video of the technique in action, filmed a few weeks ago for one of our local lifestyle TV shows: