In the very first post there is a link to a bookmark page that has loads of instructions - I think there is one on applique! If you are just adding a ruffle to the bottom of jeans, I'd say skip the ruffle foot and gather by hand. If you are doing a ruffle for a dress or skirt I'd DEFINATELY buy the ruffler!
I have the how to applique instructions from ycmt and I didn't learn anything that I hadn't already learned form the helpful ladies on this thread!
A quick tutorial:
Get you patterns by searching coloring pages. Really good site for Princesses/D!sney is Thedollpalace here's a link:
http://www.thedollpalace.com/coloring-pages/sec30-Disney.html#secLink
Trace EACH of the pattern pieces onto fusible web - I hold the patter and fusible web up to a window and trace it there. For Cinderell you would trace her hair, headband, face shape, eyes, etc. Cut them slightly bigger so when you piece them together they overlap.
Cut out your fusible web pattern pieces. Iron the web to the BACK side of the fabrics you are using. Cut the now fused pattern pieces out of the fabric. Peel of the paper backing.
Layer your fabric pieces onto your base fabric, (the shirt or whatever the applique will go on.) ironing (attaching) each layer as you go. For Cinderella start with the face shape, then her hair, headband, etc.
For the actual stitching use a zig-zag stitch (I guess it is also called a satin stitch

) set at the lowest setting (on my machine it is set a 0). Go slow and take your time, making sure you stitch over all of the edges of all of the pieces! A good first applique to attempt is the mickey head - no pieces to layer!! (also in the boomark pages.)
I hope this helps - I am in no way as good as some of these ladies, I've only done a few appliques so far. But when I did my first one I wished there were some detailed insructions too! Hope this helps. If I missed something, or am wrong on anything, I'm sure someone will be along to correct me and help you!