Ok lets sit down and go bit by bit with your pregame and see what you're doing wrong, and what you're doing right.
Runes:
Your runes are everywhere, and I noticed you have some scaling things, but really what you want is more focus on your runes.
You want 9 FLAT AP reds, or 9 Mag Pen reds. Scaling reds don't do much since you're a scaling champ anyway. You're late game, so you want something that supplements your weak early game. You're going to be building full AP anyway, an extra 18 ap or so at lvl 18 isnt going to be worth it, go flat.
You want either 9 flat armors (Yellows) or 9 flat healths. But since you're taking nid TOP often, really i'd suggest ARMOR since a vast majority of meta top laners are going to be AD. if you're taking her mid some scaling or flat healths wouldnt be a bad idea, but really, going with armor gives you the most coverage since the majority of the game itself is AD.
Seals: You want to take flat mag resistance, since you're very squishy, youre gonna want beef early, since you will be very very fragile.
Quints: AP quints are gonna be your best bet. All of them need to be AP. With 3 of them you'll have 15 ap, out the gate, and thats nearly a dorans ring, for free.
MASTERIES
Oh boy these are...interesting.
You're taking grasp of the undying which really makes 0 sense. Grasp's efficacy is reduced by 50% for ranged champions, so really you're crippling yourself for the whole game by taking it. Thunderlords would be a much better choice, since you're an assassin and your'e going to want to burst them. Even if you're working against a tank, you're going to want to take TLD.
I would go 12/18/0 taking these masteries.
Sorcery: Self explanitory. You're an AP caster, you're going to want your abilities to do more damage.
Either Feast or First Blood: Feast will help you sustain in lane but it also assumes you're in a position to be able to farm safely without harass, which will 100% be a threat to you in divisions to come.
Natural Talent: Taking Vampirism doesnt make any sense on Nid since she doesnt do a lot of melee damage, and would benefit far more from the extra ap and such.
Double Edge Sword or Battle Trance: Double Edge Sword will make everything you do hurt more, but you'll be more at risk. This again is risky, so be careful with it. Otherwise I'd take battle trance, since you can ramp up to the bonus damage with just autos and then all in with your spear and cougar when you get the full bonus.
( Cunning)
Savagery: This will help you last hit. If you're taking her in the jungle I'd probably take Explorer for the map mobility but in lane savagery will help you fight waves better.
Assassin: 100% the best option here since you're going to be facing off solo against these people most of the time, and the amount of damage you get from it will work wonders.
Merciless: Tired of them getting away with 10hp? Merciless helps with that. Sure it may be hard to get some champs down to 50% hp but once you get them there merciless helps a ton by increasing your damage significantly.
Greenfather or Dangerous Game: Take green father if you want to play the bush. Use the bush to harass and reset minion aggro, and deal auto or spear damage boosted from the bushes, and force the top laner to invest vision on the bush youre playing around, making the more gankable.
Or
Dangerous game will help you survive those clutch moments, and will benefit IMMENSLY from it late game when you look to munch the adc.
Precision: Nidalee is mostly AP but does do a bit of auto attacking esp in cougar form so precision helps, plus makes your autos sting more. This will be the way to go.
Then, thunderlords. You know what it does. It increases your burst every 30 seconds, its great, take it on nid.
I'd give more advice with itemizing nidalee in game but really I wouldnt be able to give you much solid advice. If you insist on laning as her, don't take frostfang. You lose the passive when you cs, and you NEED to be csing more. Your cs is maybe 30-40% of what is given to you. If you can focus on csing more than getting kills you'll more consistently get gold, which will help you win more games more often just by perfecting cs. It may be hard to kill garen but minions are garenteed. ;)
ALso I'd highly consider taking Nid into the jungle, since she has a lot more benefit there, than she does top lane. (Your masteries might have to change for jungle)
Some champs that I would say are similar to Nid in their kit, would be 
for the top lane. He has a similar form switch kit to nidalee, plus a long medium speed projectile, similar to nidalee's spear, and he can trade and harass with most top laners far better than nid can.
For mid I would actually suggest 
.
Anivia since her stun moves at a very similar speed to nidalee's spear, so it might be an easy transistion.
Velkoz, has about the same range as nidalee, so if you're any good at predictive aiming with nid, Velkoz would be a decent champ to learn.
If you're stuck with ADC i'd go with Varus, since his arrow and nid's spear are very similar, however his is faster and goes through minions. Also he has a root which helps in securing kills and helps with team fights, so its worth mentioning.
Also Caitlyn is similar with her long projectiles, and on the same hand has tons of maneuverability and survivability.
To recap, focus on your farm the most, since I notice your cs scores are consistently low, consider jungling as nid as well, or instead. If certain champs are giving you significant trouble look up guides on how to play THOSE champions so you at least have a better understanding of their kits and cool downs. Also, keep your head on straight, don't engage in arguements, compliment your team when something goes right, and shut up fi something goes wrong.
I believe in you. I'll be waiting for you in silver.
