I made up a notebook with the things I ate and the percentage of carbs - you might be able to find an app, but you'd need to have it with you when shopping and cooking - the tiny notebook was always there are available - and never needed its batteries charged.
You need to find out your personal level of carb consumption by testing your BG two hours after eating and reducing the carbs until you get normal levels. You might find that you have to avoid the 'heavies' such as bread rice pasta potato, and the sweet fruits. I can't eat legumes without a big reaction, so a few peas or green beans are all I can eat, but there are other things which don't cause such large reactions even though they contain the same amount of carbs.