Most leagues draft 12-18 players. A kicker should ALWAYS be picked towards the end no matter what. Someone might think, well I got my starting players for every other position why not get a great kick in say the 7th or 8th round. No no this is bad. Those middle rounds it is much more valuable to get backup players. The thing with kickers is that the top 10 in the league all score approximately the same amount of points throughout a season. Thats why there is no rush to pick one. In my recent draft, which was 16 rounds, I picked only one kicker and it was in the 15th round. Also don't worry about a backup kicker just yet for your starter's bye week. I suggest just wait until that week and drop a weak bench player.
In conclusion, get ONE kicker in the last couple rounds no matter what.