One of the builds I use for Nidalee.

Utilizes an all-spectrum nidalee build; being that she's rather tanky, high ability power, and with atmas+lich bane, plenty of attack damage out-put as well.

This build, although, most useful while in her cougar stance, is also useful for tossing some high damage spears, and healing teammates.

Pros:

Tanky.
High magic/attack damage out-put.
Great solo-top.

Cons:

Low mana/mana regen (not needed in cougar, but helpful for heals/spears)
Not much MR.

Reason for using Quints on Armor Pen and Marks on Magic Pen is due to them being at the peak of their usefulness in those categories. Since I build my nidalee to do both magic damage, and a decent amount of attack damage, I use both.

The armor and magic resist runes are just to give a tankier base for nidalee. Armor is especially helpful while in lane phase on top, and then the little bit of Magic resists are to help make up for how much the item-build lacks for her.

My masteries build 21/0/9 -- As you can see, in the offensive category, I go straight into Ability Power selections. I know that even though I build my nidalee AD and AP that with this build, nidalee will do approx 2x more magic damage in the entire game, therefor, I use the masteries to add into that a little more.

As for utilities, I like going into the mana/mana regen selections due to the lack of mana/mana regen my build contains. Also, I highly recommend getting blue buff whenever capable to max CDR, and to help pad the fact that you have no mana regen on your own.

The item build that I've created generally maximizes in doing damage, while including high survive-ability.

Nidalee's cougar form utilizes 1 AD-based ability, as-well as 2 AP-based abilities. I build the high amount of AP that I do mainly because using her two AP-based abilities can dish out a bit of damage, and with lich-bane, the AD-based ability can do so much more damage. The addition of warmog/atmas to the mix only makes nidalee much tankier, and with much more attack damage to deal.

Outside of cougar stance, AP comes in handy for heals + spears. As anyone that has played against AP nid knows, her spears hurt. Although, her heals were nerfed, with high AP they still dish out quite a bit of health, and I find them to be pretty helpful all game long.

Maxing heal first allows for better lane sustain.
Making sure to have Q W and E before 6 is essential in order to be able to use all of the abilities in Nidalee's cougar stance.

You can take traps 2nd and spears 4th, depending on your own preferences. I usually take spear 2nd just in-case a near-kill comes extremely early.

Although, traps can be very helpful with shredding armor/mr... I level them up last only because I primarily spam them for warding, and prefer to chuck some spears mid game.

Prefer Exhaust/Flash --
Even though nidalee's cougar form can leap like every 2-3 seconds, I still take flash because.. who doesn't take flash? Not only that, but it just always helps to get out of sticky situations, or confirming kills.

I pick exhaust over teleport for solo-top mainly because it gives you an edge in a brawl all game long, and with Nidalee's jump she can make it to just about anywhere quicker than your average bear.. that and blue pilling isnt as common with her high degree of sustain, she can basically bounce back from anything for a while.

Particularly like this build in ranked play because it's capable of so much in a team fight.

Starting with boots and 3 pots is typically the better route to go solo top, maybe switch to armor+5pot if you're versing a tank-plank or just a difficult bruiser champion; however, the reason i prefer regular boots on nidalee to begin with is just because a lot of champs that go top are melee, and being able to go quicker than them usually just adds a nice bit of security in your lane. Also, know that 3 pots is sufficient as nidalee's heal gives her one of the best sustains in top lane.

I like to build my warmogs and rabadons together. Usually by grabbing blasting wand and giant's belt, and then finishing out my rabadons. I like the giant's belt for the early extra health, which makes him not so squishy for gank moments and for aggressive lanes. Also, it helps to have a little extra health and some ability power after hitting 6 because then you can start utilizing nidalee's ulty poke. She can dish out loads of damage just by pouncing in, getting a swipe off, and then biting a chunk of their face off, then just jumping back out... at relatively little damage in return (usually).

Not only does the CDR boots allow nidalee to hunt down champs a little quicker by pouncing at them much more frequently, they also allow nidalee to basically dish out more damage because she can spam her abilities so much more frequently, and in cougar form, where mana is never the issue, it comes in handy to be able to do so.

The sustain that this build gives her allows her to deal her damage even in team fights while cougar'd, rather than being shoved off to the side casting heals, and throwing spears. Being able to dive in those team fights and get a few slashes and pounces in the enemy teams face gives so much additional sway in the team fights. Additionally, with lich bane, her bite does an inordinate amount of damage, as it procs and uses simultaneously. Full build, that's a nice chunk of damage. Even when just auto-attacking, pounce allows lich bane to proc right off its cooldown and dish out plenty of additional damage. Not to mention the light amount of ability power, and magic resistance that comes with lich bane, as well.

With atmas, nidalee gets that little extra umph of attack damage and durability during fights. Not only does her bite get that bit of extra damage, she gets the armor, as well... making atmas a decent item. The addition of warmogs allows that attack damage to be even greater, while, also, accomplishing additional sustain in team fights.