ADC- The ADC stands for Attack Damage Carry. This means that they are the characters you want to build Attack Damage as well as Attack Speed with, However depending on the champion it may vary and certain champs synergise better with different items. This is why you should ALWAYSlook up builds to make sure you are building properly. The ADC is a role which is centered around the bot lane(always bot lane) and is played duo with a support champion. The ADC main objective at the bot lane is to try and last hit minions to get the gold off of them as well as trade(do damage to the opponents) so you can win the lane. When playing ADC it is always good to learn how to position well so you are not easily ganked and are able to get kills. The cons to ADC are that it mainly rely's on the support as the support are the ones to make plays with their stuns and CC. Then the ADC finishing the champions off. When in team fights you will always want to stay behind your team as the ADC is one of the squishiest champion roles(weak/ low health). This also lets you peal and do damage from a far, This works well with the ADC as all ADC's are ranged. Another key objective to playing ADC is that you need to learn how to kite around enemy champions to maximize the damage you deal to them. As well as kiting you will want to learn how to duke/ dodge enemy skill shots to minimize their damage as well as maybe saving you from a death. Kiting and dodging enemy skill shots is definitely another essential to ADC as well as other lanes as it makes your lane a lot easier to win.
Key = The cost of each champion 450 1350 3150 4800 6300

Sivir
Ashe
Tristana
Corki
Urgot
Miss Fortune
Kog'Maw
Twitch
Caitlyn
Ezreal
Graves
Varus
Vayne
Draven
Jinx
Kalista
Lucian
Quinn

Orthodox ADC Champions

These champions are the more easier to play as well as ones that build similar, probably champions you would want to start off with when wanting to learn the role.
This would include: Ashe, Sivir, Tristana, Caitlyn and Jinx. These champs are easier to use because they all have a slight advantage when in lane against enemies as well as easy mechanics to understand. This means that they are easy to pick and after a couple games you will get familiar with their kit and see automatic results.
Note!: Everyone is different and prefer different champions and are better with certain champions straight away due to the way you play, so play with champions you are comfortable with before trying to force yourself to play others you may not play necessarily well.

Unorthodox ADC Champions

These champions mechanically have a different kit to a normal ADC which allows them to make plays, however this is at a cost of skill. For certain champions you can not just pick up and automatically get results from them, they take time. These champions are normally heavily reliant on skill shots, positioning or how the champion should be played youtube videos. These champions sometimes are not as strong as ADC's played heavily by professional players, which means sometimes they are just not a good pick and maybe it would be better to pick champions which are in meta. This is because when trading/ exchanging damage in lane even if you are more of a skilled player you could lose the lane due to that one fact. Although they are harder to play it feels more rewarding when playing a more difficult champion and you get results via kills and assists. So do not be put off if you would like to main or try out a champion you enjoy playing. These champions are: Miss Fortune, Kog'Maw, Twitch, Ezreal, Graves, Lucian and Quinn

Higher Tier/ Meta ADC Champions

These Champions are higher damage dealers and champions considered the hardest to play at the bot lane due to their kit. These champions are more difficult to learn than unorthodox adc champions however once practiced a good amount are highly rewarding. These champions require you to understand the basics of the ADC and be able to do everything at a moderate level, that i have mention inside the specifications. Champions: Varus, Vayne, Draven and Kalista.