Hmmm... I'd suggest using some sort of backing fabric, first of all, so that the different types of patches will all retain their integrity. If you don't back them, some will weaken and/or stretch, and then the whole skirt will lose its shape.
Also, if the skirt is EVER going to be washed, make sure that you pre-wash all the patches and the backing to avoid having shrinkage issues later. Iit depends what kind of fabric you've got --- it may be something that will only be dry-cleaned, in which case you're good to go.
Next, you'll have to decide on two things:
1) The shape of the skirt you want. if you're not experienced sewers, you should probably buy a pattern rather than try to construct your own.
2) Whether you want the patches to be regular (squares or rectangles that all line up) or irregular (random shapes that overlap). If you do regular shapes, then you might be able to sew entire strips of fabric together (like quilt blocks) and then attach them to the backing all at once. If you do irregular shapes, you'll have to attach each piece to the backing, one at a time, and you may find it easier to do this by hand than by machine. (My crazy quilt, here, http://www.craftster.org/forum/index.php?topic=7659.0
, is an example of how you'd do this.)
Once you've pieced all the patches onto the backing, then you'd assemble the skirt according to the pattern. Be warned --- it's going to take a LOT of hand-sized patches to make a whole skirt, especially one full enough to look 'period'... Another option would be to make a cape or capelet --- if you did a short one that came just to hip length, you'd need a lot less fabric and could get results even faster. (You'd have to line this, though, because the inside would be at least partly visible at times.)
Can I just say how jealous I am of your supply of bits and pieces of fabric?