When do you start buying wards, and when do you stop?

I just recently started playing ranked, and a lot of people keep on telling me to buy wards. What's a good time to start buying wards, and at what point of the game do you stop buying wards?

It depends on your lane and role. If you are support you want to start with at least 2 wards and a fairy charm. As every other role. I grab a ward after my first buy because you want to secure your lane from ganks.

As for when to stop. You should never stop. I like to make sure I always have at least one ward on me in case my support might not have one. Knowing where your opponent is wins games a large portion of the time. So do not stop warding.

You should ALWAYS buy 1 or 2 wards until you are finished with your gear.

BUT it's not always possible, so here we go:

Let's split by lane:

JUNGLE

Buy 1 or 2 when you get in the base after your first walk in the jungle. keep trying 1 or 2 every time you get back in the base

TOP

Try buy 1 at the beginner of the match or as soon as possible, recall and shop 1 or 2. Keep at least the river warded.

MID

Try buy 1 at the beginner of the match or as soon as possible, recall and shop 1 or 2. Combine with your jungle, so he can ward one part of the river and you do the other.

BOTTOM

If you are with a support, you can focus more in your gear. But you need buy some too. So when you have a spare of money, buy a couple or it and help warding dragon and river.

Here a great link for warding map