So, about to hit level 20

trimmed for brevity, but def. appreciate the info.
I don't usually ADC. Going with the standard meta, the ONLY possible adc champ I could have would be kayle. I don't own any other long-range champs that arent mages.

 List of champs I own

Annie, Brand, Cassie, Fiddle, Janna, Kayle, Morde, Morg, Nami, Nunu, Soraka, Udyr, Wukong, and Yasuo

I was considering picking up someone who could fill that role so I could learn it better just in case, and in particular I was looking at Draven, as for where I'm at now I don't see many, if at all. Usually it's Vayne, or Siv, with the occasional Ashe, Twitch, or Cait. Sometimes theres a jinx thrown in for laughs.

Def get the magic pen, armor, mresist, and ap quints first as it seems you like mage champs more.
Try to get armor seals first. Armor reduces tower hits, jungle creeps, auto attacks from EVERY champ, lane creeps damage, and ad based spells. And if you're looking for a strong ADC champ i would pick up Sivir. Shes only 450 IP and is a very strong champ.

Edit: Draven hurts a lot in general but hes very unique, to do good dps as him you need to consistently pick up his axes so hes hard to play. If you don't mind taking time to learn him go ahead but if you're looking for someone easier to play get Sivir.