I'll address your supplements query. Banaba leaf, bitter melon, green tea extracts, cinnamon, chromium, vanadyl sulfate, fenugreek, and alpha-lipoic acid are among the many dietary supplements that have been studied for diabetes management. These ingredients are rarely included in standard formulations of daily multivitamins due to the added cost and other factors. However, you can often find combinations of the aforementioned substances in various proprietary, "miracle diabetes formulas" that are sold at premium prices far beyond their cost-benefit ratios. Many of these natural herbs and extracts have shown some value in lowering blood glucose levels in laboratory animals but provide only marginal benefits in humans with the possible exception of alpha lipoic acid.
A small percentage of users have reported that it helps them "dramatically" lower their blood sugar levels but I believe that, on closer analysis, it could just as readily have been due to improvements in their lifestyle modifications. These include diet, exercise, and weight loss (particularly the reduction of BMI and belly fat). If you have the funds, you might want to experiment with them on a short term basis (e.g., three to six months) but carefully monitor and evaluate your results. Don't make the mistake of purchasing or committing to long term quantities such as the auto-ship programs promoted by many vendors as well as hucksters. Many of these substances work by exerting a modest effect on the reduction of insulin resistance but it is inconclusive as to whether they lower blood glucose levels directly (with the possible exception of alpha lipoic acid).
If your own problem is primarily one of insulin resistance, these substances "might be" of some value. I have personally tried most of these herbs and extracts in various blends and combinations. In fact, I spent well over a thousand dollars (U.S.) per year purchasing various formulations that claimed to specifically target or benefit diabetes. My experiment ended after two years with very disappointing results. Although I still take quite a few nutritional supplements, all are focused on improving
general health and
not on diabetes specifically. These include coenzyme Q10 (ubiquinol form), vitamin D3 (6,000 IU daily in divided doses), benfotiamine, alpha lipoic acid (in combination with biotin), gamma tocopherol, a high quality multivitamin (special multi-dose daily formulation), EPA/DHA, GLA with sesame lignans, curcumin, lutein/zeaxanthin/astaxanthin blend, L-acetyl carnitine, and others.