I am bronze and I made this for fun. I'm not even m7 on Neeko. This guide is just my thoughts from my games that I have played on Neeko.

Pros

Overpowered support
Great poke
Good root and CC
Camoflage in wave
Has clones + speed boost
Big *** ult
Has wave clear if wave crashes

Cons

If engaged on, can't really get out (can be solved through items)
If can't hit skillshots, no utility or dmg
Low range
No peel for adc
No sustain for adc

Arcane Comet
Nice dmg for supp
Manaflow Band
Mana good more sustain
Transcendence
More ability haste for more roots, more poke, and more slay
Scorch
More poke! More slay!
Biscuit Delivery
Good sustain for laning
Cosmic Insight
More item and summoner spell haste. Very good because you will run Zhonyas, and Hextech which need item haste. More summoner spell haste means more flash+R combos

Passive: Camouflage as things you get close to like plants, minions and your team's champions. Good for sneaking into lane and element of surprise.
Q deals magic damage, and hits another time if something dies or hits a champion. Hits up to 3 times, and later hits deal less damage than the initial hit.
W has a passive where every 3rd auto does bonus magic damage, and gives move speed.
W has an active where Neeko summons a clone and can control where she goes.
E is a root that grows as it goes through units.
R is a delayed spell that stuns, airbornes, and slams down, dealing magic damage. Can be combo with Hextech Rocketbelt engage and R+Zhonyas.

Poking
Camouflaging makes Laning phase the easiest part of the game. Become part of the wave, and when they get close, use your E then Q.

Engage
W for movement speed and clone for confusion can help you set up an easy E. Building Hextech Rocketbelt will help with engage. Hextech+R or flash+R is great engage. You could also camouflage, and then R while they are trying to cs.

Disengage
Using W(clone) to confuse any enemy trying to kill you. You can also use your clone to block skillshots if you are that much of a girlboss. Your ult is also a great disengage tool, people who are chasing you do not want to get caught in it, and you can also turn on them if you hit them.

Neeko was made for teamfights. Literally the girlboss of teamfights. She can easily camouflage, hextech rocketbelt or flash in ult, and her E goes through people, making it entirely possible for her to root a **** ton of people if they line up. All you have to do is engage with R, root with E, and Q.

Neeko is an overpowered suppport that wins most trades and has an insane amount of util. Also, if you want to sell your boots for a better amge item, because hextech can give you most of the engage mobility you need. Good luck playing Neeko.

Thanks for reading and have fun!