Vayne if you're decent mechanically (If you're bronze or silver or low gold, you're not skill mechanically.) Varus if you want the best all around. Graves if he ever gets some buff in the near future. Otherwise he's outclassed by literally every ADC in the game.
I sense a disturbance in the force. League of Legends IGN: Vave
I couldn't really get into Varus when I used him. I used him a month or two back when he was free and found him pretty boring. I didn't find him to be too powerful of a character, but I probably wasn't that good with him either or the meta changed to suit him more. Graves I played when he was free one week and he was alright. Not super fun, but also not boring. A character I would not mind playing if our team really needed someone like him for our composition or something. Vayne I have not played, but basically have heard she has a terrible laning phase, but if you survive it somehow you can become crazy powerful late game.
Good game design died when people began to think having to use outside sources like guides to get past mandatory parts of games was acceptable. - Chipsrgood555