I go a fast Mejai´s Soulstealer for fast stacks and maximum AP.
My choice of boots is Mercury´s Treads because you can run from or to your enemy faster. If you want you can buy Sorcerer´s Shoes for more damage with your spear, but I think it´s to small different.
Then I buy a Guinsoo´s Rageblade for maximum damage and Attack Speed with your Ultimate Aspect Of The Cougar, and fast tower kills.
And then of curse a Rabadon´s Deathcap for a lot AP, awesome item.
And after Rabadon´s Deathcap I buy a Lich Bane for much mana and AP, the passive from sheen is really nice to.
A Rylai´s Crystal Scepter is for much health and AP so you survive much esier.
And last item is Void Staff, for maximum damage!

Pros
Spears are fun to use
Can heal herself
Good escaper (especially in jungle)
Can trap bushes to protect from ganks

Cons
Squishy
Can be hard to find your place in team fights
High mana costs early game

For runes I go Magic Penetration Mark´s for more AP damage.
For Seal´s i go Mana per 5 seconds runes to get my mana back as fast as possible to throw my spear faster!
And Glyph runes are Ability Power for more Ability Power.
And Quintenssence I take more flat Ability Power. For me runes are not so important but I know that many of you who read this will say runes is important! And yes it maybe is. But I am not that good of LoL to concentrate on runes yet :P

Max Javelin Toss / Takedown as fast as possible. I think it´s the best skill in game and I don´t understand why Riot Games doesn´t nurf it, but it´s only possitive for us Nidalee players!
After Javelin Toss / Takedown I max Primal Surge / Swipe to heal nearby enemies or your self. And in Cougar form to farm minions in best way.
And the last skill Bushwhack / Pounce, I don´t think it´s so great so I max it last.
And ofcurse Ultimate Aspect Of The Cougar you max as fast you can.

I choose Flash because I always choose flash and think it´s so great.
And my second choice is Ignite to finish my enemy when they run away, if my Javelin Toss / Takedown is on cooldown.
Other choice is Flash and Exhaust or Ghost and Ignite/Exhaust.
Or if u want to run away from your enemy, or run to them you can go Flash and Ghost.

To farm minions go in Cougar form (ultimate) and jump into the minion wawe with W (Pounce) and then make sure that all minions are around you and you will go E (Swipe) to clear nearly all minions around you, if you want you can use Q (Takedown) to minions with more HP after E (Swipe)

I bild this build whole alone after maybe 3 days playing Nidalee and I´m praud over it.
It works for me!

// Flacecheese