I am on MDI, and I do not have a CGM. I have managed to get my A1C from a terrible 9.3 to 7.2 in 3 months. My plan is to get it down to 6.0 in the next three months.
I exercise 7 days a week, biking, weights, resistance and some aerobics. I limit carbs to no more than 75g per day.
I tested pre-meal and 2 hours post meal to figure out what foods didn't raise BG over 140. I found that I cannot tolerate any bread, pasta or grains. I am a religious carb counter. I substitute spaghetti squash for pasta in dishes that call for that. I also substitute riced cauliflower when I make mac n cheese or other "casserole" type dishes. For breakfast I eat Chia pudding and that doesn't impact my BG's at all. There a lots of chia pudding recipes available, I posted one on another thread.
If I drink a cup of coffee, I always drink the same number of ounces of water to offset it, as coffee does seem to raise my BG if I don't do that.
I also have a "Diabetes Library of books for reference". Dr. Bernstein's "Diabetes Solution" is a great book to have, as is "Think Like a Pancreas". .
(Pretty much everything I have learned to do, I learned from TuDiabetes, as I got no guidance at all when I was diagnosed 4 years ago.)