How many control wards should I buy per game

I use control wards mainly during combat, e.g if someone walks into a bush to auto them without getting near or to control ward a important bush and play around the vision before/during the fight.

I find it very useful in a lot of situations but how many should I buy before it becomes a detriment.

I buy around 5 per game, that’s like 375 gold. That is quite a bit. Is it too much?