My name's Jhonyne Im new at MobaFire,im a Brazilian and i play at Br Server i'm a experient Kalista user with High KDA Ratio and normally im the one that carry the game either early or lately!
Kalista is a really good champion With A long Time to Master it, i found her an basic but Hard champion with high kiting potential and Peaks at 1v2 ,she can carry games alone for sure if you manage to play it correctly.
The difference between one Adc to Another Is Their Farming Skills,Even if you are 0/2 and the other adc has 2 kills but his farm is way lower up to 30 the game is still balanced.
Kalista Kite can be used both to defend as to atack,along with vayne one of the best champion to kite offensively ,she's also really hard to get ganked Post-6 because of her ult that can be used in many ways either to stop the gank or to save a suport that got all focus on,as well her W will tell you if it finds some lost jungler around the map :P .
So Kalista for me is=Powerfull kiting potential/unlimited warding and a life saver the only thing she lacks is CC and life(Of course) So geting a "Focus Me" tanky Suport will get to win 90% of the trades.

First find a high potential early game tanky suport,Like leona/blitz/tresh/alistar.....
All of these can give kalista a Strong Early game potential, that in my opnion she lacks a lot,just farm early game and wait for a good chance to atack,blitz/tresh=hook,alistar/blitz=knockup,leona=CC,all of these will grant you a good chance to lay your spears,usually you're gonna win the only ones that you shouldnt really trade this way are jhin and Draven because of their burst ,jinx have a high early game burst but she lacks mobility and probably wont try a trade,= jhin and Draven can turn around the trade with his high burst.
In Late levels there's a trick with kalista that's the AA+Q combo (doubleJump) you can do either to the front as to the back train that a lot is very helpfull.
I Personally dont use q for harass i use AA or i dont harass ,cause kalista is very reliable on her Q either To run or to get a kill.

A good thing that you should do is get level 2 First and become agressive with the enemy level 1 thats why Those early game support are really nice To kalista,As level 2 you have 70% of your Trade "Peak" (level 6 of course),Focus farm dont worry about Losing a Trade wait for your Jungle ,3x2 is better than 2x2 dont you think?
Her farming pottential is good as weel as she can secure farm with her E without wasting mana.

Pros=High mobility,High kiting potential,Low Gank Sucess,High atack speed,Usefull skills for last hiting,Good iniciation.
Cons=Very Reliable in Tanky supports,Hard To Master.

Having a Tank as Support Is Really Usefull,She Does not Get 100% by having a utility support such as karma,Morgana And others.
Saty behind your Front Line and if it goes away dont worry start kiting like hell,she's really good 1v5 without lots of CC's.

Learn to farm.
Learn to kite with keyboard.
Learn postioning.
Learn Trading.
Learn to use items(Though you will only used ruined king but its a really important item.)
Learn how a suport and a jungle Works.(Play some games or watch some videos)
Dont try to copy someone play your own style getting tips are ok but copying is just Stupid.

Most Important thing for ADC's a good farm diference gets a high Advantage Mid/late game so focus farm and objectives.
This is the thing i teach most my friends is farming,take a time and train farm without runes/talents and skills =that's freaking hard ,and try to never miss minions ,also get different wave's forms so ask a friend to help.
A easy way of farming is get the first 3 minions,when it get's to the big one farm the minions magician and last hit the big one,whenever i did 6.7 higher Cs per minute i won the match or finished as the mvp with most kills or whatever.

Ruined King Is a good item To Start But you can Play agressively as Well With Infinite Edge.