The amount of pieces of gnocchi per person is around 20 gnocchi per person or around 100g which is suitable for a starter.
A good general portion per person of gnocchi is between 100 to 130 grams of gnocchi per person.
Although the exact amount of gnocchi per person will also depend on if it's a main dish or a starter dish and even the appetite of the people eating the gnocchi.
And how hearty the sauce is also factors into the amount of gnocchi per person.
A serving of 6 oz to 9 oz of 170 to 255g of fresh gnocchi is often good for a main course.
Although for a smaller course or portion, then 20 gnocchi per person which is around 100g is often perfect for a starter.
As a main course it's best to have around 130 grams on the higher end for the recommended portion.
For a starter dish or side dish then the smaller serving such as 6 oz or 170g of fresh gnocchi, or around 20 pieces of gnocchi is often suitable.
Gnocchi is also often served with sauces, so you should also consider how filling the sauce is gonna be as a very rich sauce can allow for a smaller gnocchi portion.