This is a very simple build, especially directed at beginners who have hard to decide / don't know what to buy.
This build is very broad, and can be played in most games.

AP

I like this Summoner Spells most, because its a good run-away combo, but also good for chasing down your enemies easy and safe.

You can play Support with this build as well, just pick Clairvoyance instead of Ignite

AD

These two spells are absolutely the best work for AD Nidalee. First and foremost, Ignite deals a lot of damage, but good against enemies that can heal themselves, as it removes heals by 50%.

AP

Sell Doran's Ring in late game to get your Void Staff, and maybe sell the Moonflair Spellblade to grab a Will of the Ancients or Zhonya's Hourglass

AD

Sell your Wriggle's Lantern to grab a Last Whisper

AP

Why I pick following runes:
- Greater Seal of Scaling Mana Regeneration = This is the best Seals (mana-reg) because you will use your spell Javelin Toss / Takedown and Primal Surge / Swipe very much, and this will help you to not go out of mana.

- Greater Mark of Magic Penetration is because I think the magic penetration is very important, but you can change to Greater Mark of Scaling Ability Power if you feel you are in dire need of Ability Power.

- Greater Glyph of Scaling Ability Power for extra ability power, enought said.

- Greater Quintessence of Ability Power for extra ability power.

AD

:
Why I pick following runes:
- Greater Mark of Attack Damage Flat AD runes (to be strong in early game).

- Greater Seal of Armor Additional armor is always good, because you will be in many teamfights with AD's.

- Greater Glyph of Magic Resist Additional magic resist is good against Abily Power champions.

- Greater Quintessence of Attack Damage Very good, extra attack damage.


Comment: I have chosen to use the flat (not ***/per level) AD runes, because it very well in the early game.

AP

When you play AP Nidalee, you should be very active with your heals, since you have a lot of mana-reg runes, your mana will restore very quick, so do not be afraid to heal your teammates.

AD

You should try to avoid fights until level six, because you are not strong enough to deal much damage to the opponent as AD nidalee.
But when you hit level six, you are very strong because you have flat AD runes.