Chromium is the most important nutrient for type 2 diabetes. Chromium is what keeps the insulin receptors open. But picolinate is not near as effective as chromium polynicotinate. In fact chromium polynicotinate is 300 times more effective than chromium picolinate, and is the same cost. Several companies sell it. Nature's way sells it under the name GTF chromium. Solaray sells it under the name Actichrome. I believe NOW Foods also makes one. Recommended dose is 200mcg 3 to 4 times daily.
There are a lot of herbs that can help, but dosing will depend on the form you use. Capsules, powder, extract.....
One of the herbs I would really focus on is gymnema sylvestre, which is a Sugar blocker and helps with insulin sensitivity.