whats the best nutrition plan for a diabetic?

keeping your blood sugar under control is the key to bulking up. As long as you take the correct dose of insulin for the food you eat you should be able to gain. I hope you have an insulin pump. My pump has made managing my diabetes much easier. Ask an M.D. about supplements,

Your insulin forces nutrients, sugar, into your muscles. You should talk with a doc or diabetic counselor about what type of insulin to use and when to keep good muscle growth going. Usually fast acting calculated to cover the carbs you ate. This should within a half hour of your heavy workout. You need protein and carbs and insulin to feed the muscle.
Some say OK on creatine some say no. Most who say OK are talking about type 2 people. I would not do it if I was type 1.

As far as diet is concerned I would suggest you and your parents read Dr. Bernstiens book Diabetes in Control. it is an approach that is hard but has worked very well for a lot of type 1's.
You can find most of the book on line.

http://www.thebernsteinconnection.com/