Tough question. I can't remember when I started testing it out, as I had a lot of fear having to use canes to walk on knees full of ground glass causes a great deal of lasting fear, that lasts long after the worst of the pain has receded, and the canes have long been put away. But I started iwth a small amount, and I did get a little joint pain at first with potatoes, so I stopped eating it, then tried again after a while. And when a little was ok, I just gradually increased, just every few days at first would be my guess, then a ilttle maybe every other day, then every day, then a little more. Now I can eat 100 grams up to twice a day. And am experimenting with increasing that.
I am being much more cautious with tomatoes and peppers, as they were much worse to me than potato. But I've had a little here and there without noticing much if anything.

My husband gets hives and ear aches/infections from nightshades, but he has been reducing PUFA for a while now (a few months?) and though he hasn't reduced them nearly as much as I have, he is now tolerating some potato, some ketchup, too. He gets the ear thing from dairy and beef too, but has been able to eat haagen dazs ice cream and some cheese also without more than a little background buzzing in his ears...........he is quite pleased as he has had to be "off" these things for way over 15 years now. He is planning to try a little green pepper next. Oh, forgot to say, he has even had some of the grass fed beef we got and not had any increase in symptoms too.

It really is great to be able to broaden one's diet and not suffer severe pain for it........!!!
sol