Personally, my preferred champions look something like the following.
Top:

Jungle:

Mid:

If I had to recommend any one champion who may benefit your pool, I would probably recommend picking up Irelia for the purpose of countering ranged champions in top lane and assassinating the enemy backline.
Alternatively, Jayce, Lux and Ahri are great mid-laners depending on what you want for your team. They are all rather safe and versatile, fit well into most team compositions and have few bad match-ups.
- Jayce provides a great snowballing potential and poke while filling the niche of an AD mid-laner. He synergizes greatly with armor penetration items (including Youmuu's Ghostblade, Black Cleaver and Lord Dominik's Regards), which lets him handle both squishy and durable targets rather well.
- Ahri is a mobile kite-oriented mage who possesses CC, waveclear and sustain. She has very few bad match-ups, is great at roaming for kills after level 6 and is very difficult to pin down during teamfights.
- Lux provides a lot of utility and burst damage while remaining very safe. She is great at teamfighting and sieging, but her dueling potential isn't fantastic.