is difficult to play because he relies on slowly chipping away the enemy health from great distance. He has no escapes and is incapable of melting the enemy before they get too close to him unlike some other ADC's and with the amount of mobility and gapclosers today that weakness is amplified.
Think of him as artillery. He does high amounts of mixed damage that shreds both tanks and squishies, and by spamming his R he can force an enemy team to initiate a fight even when they are at a disadvantage, as a team can only take so many R shots from him before they either have to recall or go in to kill him. He is far and away the best siege ADC in the game, as his W allows him to outrange turrets, and his R makes turret hugging impossible. But he usually needs a tank support to offset his insane squishiness, and he needs a team that knows how to protect him, and also wait for him to land enough R's before initiating a teamfight. Both of these are not reliably found in solo queue, especially in low elo, and unlike most ADC's Kog'Maw will still have trouble carrying even when fed if he doesn't have a good team. Like a support, he really relies on the team to make use of his abilities, if his team is no good then carrying as Koggie is going to be very difficult.
are
-based ADC's, they rely much more on casting abilities than basic attack ADC's which are based on
. They are usually better against squishy targets, as they have burst which allows them to kill squishies before they can react, they usually cannot be defeated with thornmail, and have dash mobility which buys them time in-between cooldowns. However, their lack of sustained damage means they struggle against tanky opponents, whereas their
based peers have the sustained damage necessary when dealing with something like a fully stacked
.
is somewhat of a hybrid of these two types of ADC's. He has fair burst, and also decent sustained damage, while still possessing dash mobility so it is viable to build him with either
or
as his core item, or even a mix of both if you are experienced with him. He is also the most durable of the ADC's, so he tends to stick around in teamfights for quite a while.
I don't know much about
, his kit is weird in that he scales well with both attack speed and ability power, yet also works well with attack damage. His kit feels all-over the place, he seems to be a champion that is versatile in that his kit can be built in many different ways, but isn't outstanding in any one build (kind of like
). Most I can say try him out, I have seen people build straight AP Varus and do quite well, I would imagine Nashor's tooth would work well with him.
is a very underplayed ADC, but at the same time the people who do play her know exactly what they are doing, and I see too many pentakills from these people so she is worth trying out if you get the chance. Also, people often don't know how to deal with low pickrate champs like Quinn because they rarely see her in play, therefore often don't know what she is capable of.
She is somewhat like Graves in that she has both burst and sustained damage, and is slightly more durable than most ADC's, but trades instant dash mobility for infrequent yet very high speed, sustained mobility in her bird form. Both her sustained and burst damage is somewhat lackluster, but she has the highest utility of all ADC's (somewhat like Ashe). Her blind can save her team from the wrath of a fed enemy ADC (assuming they are
based) and allows her to go toe-to-toe with most ADC's if she can land her blind, making her somewhat of an anti-adc. Her knockback is excellent for interruptions, saving her knockback for the right moment can mean the difference between victory and defeat when facing a team with devastating channeled ults like
. Other minor channels, like
's meditate, can also be interrupted, and as a Yi player I can tell you that interrupting my meditate can turn a potential quadrakill into a dead YI in the matter of a second. Sending valor to scout an area gives amazing vision to your entire team, and when timed right, gives your teammates the vision needed to make their best plays and pulloff a flawless ace.
I know you said you don't like
, but I recommend you try her out, as she is perfect for learning how to farm. She has a very short autoattack animation and very high projectile speed, so there are fewer delays you have to account for when last hitting with her, as opposed to some other ADC's (Ashe's attack animation is problematic in this regard). Her long early game range allows you to take less harass while farming, that way you can learn how to properly last hit without concerning yourself about the harass from the enemy. Once you have increased your last-hitting skill, you can then start learning how to maintain maximum farm while dodging harass. Right now you are probably playing with a short-range adc and are taking a lot of harass while you farm during your laning phase, and you are not learning effectively how to last hit OR dodge harass. When it comes to League mechanics, it's best to learn one step at a time ( I didn't do this, which is why I am not very skilled considering how many games I have played. Take it slow and take one step at a time or you will end up wasting your time and not learning from games).