Gluten is vital wheat gluten, and can be purchased at health food stores and through the King Arthur Flour catalog. Also, ascorbic acid, malt ( liqud and powder ),
and lecithin can be bought there, too. There is also a product called Bread Dough Enhncer that is a combination of gluten, ascorbic acid,and malt powder. Gluten makes bread lighter in texture, ascorbic acid helps the yeast work more vigorously, and malt helps give bread a nice rise and flavor. Together, they act as a dough conditioner, and ca make the difference between a glorified "door stop" and a light, even-textured loaf. Lecithin helps keep bread fresh longer, and helps retain moistmess. There are no hard and fast rules on amounts. I have experimented and made my own formulas to suit my taste. I recommend the Bread Magic series of bread machine machine books by Linda Rehberg and Lois Conway. Also, the folks at King Arthur's catalog ( 800-827-6836) are very knowledgeable and can guide you as to amounts,etc., which space doesn't permit here. Good luck!