I agree with Helen that getting your BGs under control is more important than gaining weight, but have additional thoughts. For starters, the higher BG #s can actually cause weight loss. In my personal experience, the weight loss didn't stop until long after the blood glucose numbers stabilized. Also, are you positive that you're not LADA (slow adult onset T1)? Although there are certainly skinny T2s, your body frame suggests checking into testing for T1. LADA can be handled with diet & exercise for a while, but not long-term. And a definitive diagnosis is always a good thing to have.
As far as diet suggestions, are you cooking your own food? If so, consider finding a website that allows you to input your recipe and find out the nutritional information. I usually use either the caloriecount or nutritiondata websites. That way, your can figure out a good portion size and know what your carbs, proteins, calories, and fat are. You can also tweak your own recipes a bit. Like I made aloo gobi the other day, but used more cauliflower, less potato, but kept the spicing the same. For gaining a bit of weight in the meantime, you might want to try snacking on some high-fat, high protein snacks like nuts or sunflower seeds.