Im by no means a expert but be carefull with switchgrass it is great cover but very invasive. If you plant much for forbs the switch will overtake them. I like Big Blue, Lil Blue, Indian grass, Side oats, canada wild rye and then as many forbs as you can afford. The Grasses provide great cover some food value and the forbs provide color and food. Buy only local genotype seed it might be more expensive but will grow better and produce more seed than inferior/non local seed . A couple great books are, Restoring the tallgrass prairie by Shirley Shirley and Tallgrass Prairie Wildflowers by Ladd/Oberle.