Although there is no hard and fast rule here, I tend to abide by the amount that could fit in a smoker box. This is usually about 5 ounces of chips.
Keep in mind that things like temperature, smoker size, and cooking time can affect the rate at which your chips burn.
Start with 5 ounces, and if you find that you are having to replenish them too often (and disrupt the internal temperature of your chamber), or if they’re not imparting enough flavor on your turkey, then add more.