I currently main Zed, Ezreal, Master Yi, and Twisted Fate. Since it's my birthday (Wohoo!) I wanted to get a new champ, so I would love some recommendations. I'm looking at Lee Sin, but i have no clue as to what other champ I want/ should get.
"Jesus declared killcams unholy when he found out that his was over 2 hours long and directed by Mel Gibson."-GeneralKenobi85
Frankly i would just continue using the champs that you currently have and try to play against every possible match-up. But, if you really want a new champ I say buy Rumble and Kha'zix. Both are really fun and have pretty awesome mechanics.
Rumble uses no resources but his moves make him over heat, so you must watch that. Kha'zix is just a crazy fun assassin with unique evolvong techniques that can jump onto squishies and destroy them like Zed. But unlike Zed, a Kha'zix with evolved wings can have his disengage/engage move reset upon kills or assists. It's similar to Tristana's W.