It depends. The more time and effort you put in the sooner you'll see results and the less time and effort you put in the longer it will take to see results.
1-3 1 if all of your teeth have fallen out and then you get a molding and 3 if they havent fallen out yet but 1 at the least maybe more than 3 if your teeth are really bad and they all havent fallen...
in order to get to pewter city you must have beat all the gym leaders in kanto and johto so all 16 badges and then go to the cave and the boy will move letting you go through the rout and get to...