This depends on your basal metabolic rate. If you're really small and burn a lot of calories it helps control spikes but you can't run a marathon then go eat donuts lol I'd say don't go over 100 to 150 carbs a day but that also depends on your caloric intake. If you eat 1,800 calories you need usually half those calories in "good" carbs to sustain yourself. You should speak to a diabetic nutritionist or your Dr before making any decisions but there are a lot of things you can research online. Good luck!
Oh, carbs give energy to fuel so before and after a workout is a good time but youlle be eating them across the day but by bit most likely unless you just eat them all for the day at 10am then eat nothing but chicken from there on out and nothing else lol