I have a handful of ADCs that I really enjoy but my true love as far as ADC goes seems to be Ezrael.

I have Sivir, Vayne, and Tristana as backups, but my question is - As an ADC is their any particular reason for knowing more than one? Generally it seems like it's your Supports job to poke, setup kills, ward, and defend you..while your job is just.. CS, and get kills when they come up..

The question is: Can you just stick with 1 ADC, aside of being banned, and be successful? Can ADCs even be counter picked? Are there certain niches that other ADCs support?(Aside of Double AD teams with sivir)

Ultimately: How many ADCs should you learn, as an AD carry?

Learn them all. Excel at a few. Master one, maybe two. Unless you plan to go pro, in which case you should master them all.

1. Play until you know the basics of them.
2. Learn their advanced tactics.
3. do 1 and 2 with every AD carry.

It's great to know as many champions as you can, no matter what role they're in. Knowing a champ allows you to easily counterpick against it as you know its strengths and weaknesses, plus the more champs you know, the more versatile you can be in a role so that you can easily get a good synergy between champs.

Example: Any time I support or ADC, Im always asking what my lane partner is going with. If I'm ADC, and they go Taric or (preferably) Blitzcrank, I'll pull out my Vayne for an easy first blood from dual stuns (and in Blitz case, a nice lane mate to zone them out while I farm). If they're going Sona, I'll pull out Kogmaw for the poke/sustain between us and a passive, but pokey lane. Of course, these are just a couple situations. Ashe, Caitlyn, and MF are 3 more ADCs I know fairly well and I can pull out whenever needed.

The more champs you know, the better you can fill a role, the better your chances of winning.

The first part of this is not 100% true, but I suspect you know that. If you play as Ez then you should know that adc can poke right along with the support, especially in certain lanes (Sona/Ez is a good example).

I feel like everyone should buy wards. Does a bigger burden fall on the support to ward? Yes, of course. But if everyone wards then it spreads the pressure around and you get more map vision.

While yes, Ez CAN poke - it's very mana intensive, and unless they're positioned just god awfully, he can't realistically poke. Sure, poke when you can - but ultimately that job falls to the support. It's familiar to Blitz - yes he's awesome...when your opponents don't know how to position. Obviously this changes on games, and at my low elo I'd obviously be poking along with my support, and I do, but I've already seen a few games where I never got a chance to Q in lane without Eing first(and there I got first blood, that my support poked down to 50% for me. )

I really don't think ADCs should buy wards. I main mid, I play top occasionally, and I play support occasionally(I hate jungle), and I do feel that both top and mid have the obligation to ward - and I feel pink wards don't go amiss in top, but I feel the ADC should save his gold for getting to his end-game ASAP. While Supports, and Jungles win games - ADC is the primary tool that they use.

But moving back to my OP: I don't think my fundamental question came to light:

Why should you learn more than one ADC? or said another way: When would you pick a different ADC? Ignoring for a second low elo, or pubstomping niche teams(like Galio/Amumu Galio/Orianna/Annie MF Sona Malphite), in what scenario is it better to pick..say Ezrael over Kayle or Graves over Miss Fortune?

Oh god Kayle is NOT a bot lane ADC. Please don't ever try to play her as such.

That said, it depends on the enemy lane and your support. In general, burst lanes beat sustain lanes, sustain lanes beat poke lanes, and poke lanes beat burst lanes.

So Graves/Leona would beat Soraka/Ashe, but would lose to Ezreal/Sona (Given proper play, of course).

No you have it wrong. Every ADC plays different in every different matchup.

For example, as draven playing against ezreal you want to poke a TON with W+Q combo not just let your support do it. With Caitlyn one of your main jobs is to poke. Every ADC and every matchup make it different.

ADCs can be counter picked. It doesn't matter AS MUCH in lower elo because a lot of people don't even know what ADCs counter who or how they counter.

E.g. Draven counters Ezreal
Caitlyn counters Ezreal
Sivir counters Caitlyn

They're not hard counters but one side is definitely better off than the other.
And obviously if you're going to main ADC you should learn all of them. I would prioritize buying graves and Caitlyn because those are two really well rounded ADCs I think.

You only really need to learn 2 or 3 due to bans and picks. Know what every adc does, but if you got a good case with 3 of them, just know those 3 like fat kids know cake and you'll be fine.

I honestly only know two adcs pretty okay and it gets the job done. The only reason why you would learn more is if the opposing team knows you and hates you so they ban only your champs.

Play Ashe if you know your team is likely not going to be good. She can farm easily and change the game after lane phase is over. She is an uber snare that is easy to CS and poke enemies with.