Which 4800 Champion should I buy?

I have no idea where to put this, but I'ma stick this here. I play mid and ADC more than anything and am decent in those roles, but I also very rarely play top, supp, or jungle and would like to start playing those more. I'd like to play a top who could also jungle as well, so I can practice two roles. So, yeah. I play top as Teemo, Riven, or Jax (sometimes Mundo.) I've only jungled as Shaco (did decent), Fiddlesticks (not as decent), and WW (very not decent. Lol). My ADC mains are Miss Fortune, Vayne, and Twitch. My mid laner mains are Teemo, Heimer, Ahri, and LeBlanc. I already have Ahri, Kennen, Riven, and Vayne. So which 4800 champion should I buy? :) Thank you in advance for the help. (I'm including a poll, so I can keep up with the champion recommendations. They really only include the top 10 most recommended I've seen, but I included my mains, so that the recommendations can be narrowed based on the champions I played - if they even help narrow it. Lol.)