How to earn candies with the new Pokemon Go Buddy system (distance list for each Pokemon)
You can now choose a favorite Pokemon as a Buddy to walk alongside you in your endeavors (just hit the hamburger menu for customizing your character, and choose Buddy to assign one). Not only is it cool to have a Snorlax towering behind your back when you stroll the streets, but those are very rare to find if you don't hatch them from an egg, and walking with your Buddy makes it find its own candy now and then.
We say now and then, because each Pokemon has to walk different distances to collect a candy for its own arrested development, and in the case of the Snorlax it is no less than 5km. A humble Pidgey will command just 1km of walking around, of course, so it really depends on what you need to evolve. Unfortunately, you can't know how far you have to walk with each Pokemon before assigning them as your companion, and that erases any progress you've made with any previous Buddy, so here's a handy list for your strategizing pleasure.
Mr. Mime- 5km
Nidoran (f)- 3km
Nidoran (m)- 3km
Seaking - 3km
As you can easily grasp, the rarest and strongest Pokemons have to be walked quite far to get an extra candy for the type, but, if you have only had one Snorlax hatched out, maxed it out down to one candy left, and there are no others in your vicinity, the Buddy system will be a godsend. Ditto for those rare Dragonites that blocked Central Park not long ago.