How much weight will I gain with 200 calories per day?

That's dangerous to eat only 200 calories per day. You probably don't want to hear this, but you'll regret it if you do it. Your body needs at least 1,200 calories just to survive, and you'll screw it up by eating less than that. You're probably going to lose weight at first (mostly muscle), but then you'll end up gaining all the weight you lost back and more.