Ezreal is going to be the safest to answer your question, but I also feel it's important to tell you something else; in low elo people won't peel well, but people also won't focus you well either which mostly cancels itself out.
If you can't survive well enough in lower elos you also won't in higher. Keep in mind a good support player will be thinking to them self how fed you are/ important to win so they can determine if they should even bother peeling for you or instead try to support your midlaner or some other fed player on your team.
There will be alot of times where even if you think you are important enough to protect more often than not the support will still not peel for you; that doesn't even mean you're support is in the right for doing it but they still won't do it most of the time.
best adc to learn the mechanics I would say is caitlyn though, because of how she relies almost entirely on auto attacks. Jinx is easier to snowball games with, less well rounded, but also good to learn for the same reason of almost entirely relying on autos to contribute. Vayne sure, but you'll either be punished to hell when she's not meta, or it won't matter much when she's broken.