Usually not long at all. In my experience, 24 hours is the general MAX. Most times with me, though, within 6 to 10 hours.
Ok so let me provide a little more details since i want some more information on this.. On Campaign Summary i can see my campaign and on Current Status it says Active.. Now when i go to the adgroup etc etc i see the keyword and they say active too but when i click the little icon next to the keywords i get this: :/ Any idea why this happens? I am still on the review process? :/
If you want your ads to be shown as soon as in 15 minutes , go in edit campaign under campaign summary and here choose accelerated radio button