Well, your project is certainly monumental.....something I would never think of doing.......It is so much easier to go to the local LQS or Walmart or wherever and purchase new fabric for a project...or just to buy it because you like it and worry about what it will turn into when the time comes. I would sooner leave the clothes at Goodwill for the people who really need to purchase clothes at a reduced price........I do go to the local Goodwill......ours, it seems, does not have any fabric donations, not yet anyway...but I love to look at the dishes, glassware...sometimes pick up an odd serving dish or piece of stemware......
As far as fav authors of quilt books.....Eleanor Burns is great for beginners......go to Connecting
Threads website for good books of various types of quilts and their prices are always good......
...and BTW I bet you have a great collection of buttons now that you have cut up all that clothing..........those would look good in centers of yo-yos, oops!!! another project........