Wow, I don't really like your doctor's plan. Lantus is a basal insulin that lasts up to 24 hours. It isn't something you want to give PRN but on a set schedule. Many patients take nothing but Lantus. Others require metformin as well.
The alpha-glucosidase inhibitors prevent the digestion of carbohydrates. They are taken before each meal. They are most useful for reducing postprandial glucose since they prevent the conversion of carbohydrate to glucose. With less glucose available for absorption, the glucose available to go into the blood is lower. Since the carbohydrates aren't digested, they remain in the colon where the intestinal bacteria work on them and can cause gas, bloating, abdominal pain, flatulence and diarrhea. This is the number one reason people stop taking the drug. Depending on the diet, they have the potential to lower A1C from about 0.5 to 1.0%. They are contraindicated in any kind of intestinal disorder (irritable bowel syndrome, Crohn's, etc.) or liver disease. Generics are available but they aren't a lot less expensive than the brand names (Precose, Glyset).
The amino acid derivative nateglinide (Starlix) does not have a generic. It works by helping your pancreas release more insulin and is taken beofre each meal. It is not as effective as glyburide and some of the other oral agents. I've never had a patient on this, so have no pointers to pass along.
The dipeptidyl peptidase-4 inhibitor sitagliptin (Januvia) also works by regulating insulin levels. It is not approved for use with insulin.
Repaglinide (Prandin) is taken before each meal to increase secretion of insulin. It binds to the beta cells of the pancreas and has very short duration.
The last part of your feedback comments were cut off, so I can't remember exactly what types of drugs you knew about and which ones you don't. Since you are taking metformin and glimepiride, I assume you understand how they work.