Much of determining a personalized nutritional program that works....is going to be trial and error. Zone gives a good place for many to start....from there people transition to a Paleo food approach (as they know portion sizes already in their head)....and then some may experiment into different plans (IF, Warrior Diet, etc.).
As a diabetic, I would say quality of food is of course a priority and avoiding processed carbs.
Keep with what you are at if it is working, change things up little by little if it is not. Then work you way into experimenting with different approaches once you feel comfortable. Too much at once may just set you back (or could be dangerous with existing medical conditions).