Nidalee is one of those really unique champions because of her ult which gives her a new set of skills. She can be a really big damage takny AD top lane, or that really amazing poke and support AP.She can jump over walls, throw those long range spears to get those ones with just a little health after last second flash, and the master of escape and chase. She's one of the more difficult champions to play so, if you pick her up, good luck and find out which one is more of your playstyle.

The difference between AD and AP Nidalee is that AD is more of a carry while AP is more support. If you're AD, most of the time you will be in cougar form doing burst while AP you're mostly in human form poking with spears and healing. So, if you like to be the one in the middle of the team fight going after carry, go AD. If you like poking and being in the back hitting spears with tons of damage, go AP.

AD Nidalee is a really great counter to many top laners because of the fact that she is range, especially if they dont have sustain like Riven or Shyv. If the other character doesn't have much sustain then just keep harassing them. On the other hand, if they have sustain or outdamage you, like Warwick or Vlad, don't try and do too much harassing because they can just harass back and the trade will most likely go in their favor. Most importantly though, KEEP FARMING. Made famous by HotshotGG, Nidalee is usually always just farming and pushing top.
For items,start off with boots and health pots then, your main items are Merc treads if they have a lot of CC or Ninja Tabi for the heavy AD teams, and Trinity Force which is your most damage item. Doran Blades can be useful because it does give both AD and HP which is important so grabbing 1-2 if you're behind or just need help with last hitting or having a bit more harass makes Doran Blades really good. The rest of the items are mostly situational. It all depends on the other team if they get fed or not. If their AP is a burst damage who gets really fed, then go for Banshees which makes it harder for them to focus you down. If they're more of an AD problem, build health and armor because you're going to be the one jumping in the middle of fights as cougar. Quicksilver sash is something you should only get if they have people who rely on their CC like Warwick, Kennen, Skarner, etc. If your team isn't losing by much or if you're ahead by a ton, then just getting more AD can make you more of a threat and be able to focus their carry fast.

Pros:
-Great poke
-Counters many top lane champs
-Can snowball really well with a 1-2 kill lead
-Steal enemy buffs/camps pretty fast

Cons:
-If they pick a counter, it's really hard to win without ganks
-Heal doesn't give that much
-Get focused really hard if you jump in too early

AP Nidalee hasn't been played very much since the heal nerf which really hurt her. However, she is still viable. Her heal is still one of the best in the game which can be game changing in team fights, the attack speed buff is also really good if you give it to the AD carry. The reason AP is still viable is that she's the queen of poke comps. Her spears do so much damage from such a far distance which makes the inhibitor turrets really hard to get. In my opinion, AP Nidalee is more fun than AD, but it is also a bit harder because you're changing more between cougar and human form than if you're AD.
For items, the first item you need to get are your gold /5 and ROA asap. If you can, buy a philo stone first with a mana crystal for the ROA. Then, get a HoG with another ruby crystal then build a ROA immediately. You need it because you need the mana and health otherwise you'll always be OOM and too squishy. The next item you need are your tier 2 boots. Mercs are really big on Nidalee players because she needs to avoid those CC to get to a brush and escape . Tabis are also good if they dont have much CC. Sorc boots are viable though if you want to be more of the AP carry rather than a more supportive roll but, get them after you get deathcap. After boots, go for that deathcap as soon as you can. They will make your spears do those godlike damage that Nidalee is known for. After deathcap, the rest is situational. Since youre more of a support, turn your gold /5 items into a shureliyas or randuins depending on the other team. However, you will might just sell the gold /5 items to get something you really need. But, the philostone is really important because of the mana regen which you really need if you don't get blue all the time which you NEED before any team fight. The worst thing for any Nidalee player is going OOM and not be able to do anything. If your support already got these items, then you will most likely sell them to get things you need, whether it be you need more health,MR, armor, etc. If your team is ahead though, then just go for that more AP to be more of a threat if that's your playstyle.

Pros:
-Huge burst damage from far distances
-Good heals
-Fun to hit those farthest point spears

Cons:
-NEEDS BLUE
-NEED THAT 40% COOLDOWN REDUCTION

I have seen people get them on Nidalee, and I have also gotten them but I feel that there are just better items. Wriggles cost too much and you have your traps which can be your wards so just put traps in the right places. Also, it doesn't really give you much AD and the lifesteal isn't that great. The only con i can see for it is that you can take down dragon and baron faster but, sheen can already make taking down neutral monsters fast. Archangels may sound like an item mandatory on Nidalee because you need mana constantly. However, you're going to always be getting blue buff and ROA gives you enough mana to win team fights and poke if you're playing smart with your mana. So, in my opinion, these items are more for the beginner Nidalee players because they're just helpful and make things easier but, they're not worth the price for them in my opnion.

Nidalee is pertty hard to play if you compare her to other champions. You have to get used to self-casting yourself with your e because you'll be doing that a lot whether you're AD or AP. Also, hopping walls are a big thing for Nidalee. They are how she gets to places faster, being the escape queen she is, or chasing down people who flash over walls. You should really go custom game and just practice hopping over walls. Trust me, they do make a difference. Lastly,spears are usually not that hard to land but, one thing to do with spears are to throw it then cougar and jump the opposite direction. Doing this makes you farther from the spear which causes it to do more damage which can get a kill where it wouldn't have if you were standing in the same place.

Thanks for looking at my guide! Hopefully it's useful to you guys because I use Nidalee a lot so I thought it'd be helpful if you're new with her or just need a little bit of help.