Mate I've gone positive KDA in a crazy number of games recently, with mixed results
Got my champion pool pretty much set now (except for counters of course)
Top - Nasus,Darius, Singed, Riven, Mundo
Mid - Kayle, Veigar, Zed,
Jungle - Udyr, Khazix
ADC - twitch, Lucian
Support - Thresh, blitz
Mains in bold. 8/3/9 KDA average for udyr across 60 odd games ffs
Mine's also quite good, considering I mainly played support or tanky jungles for most of my games. Back to maining adc now though, seeing as a few of my mates play support as well, and I used to do that in previous seasons anyway.
My choices would be, in order of preference:
Top - Lee Sin, Jayce, Renekton, Olaf
Mid - Zed, Malzahar, Orianna, Situational
Jungle - Lee Sin, Maokai, Situational
ADC - Lucian right now, favourite is Ezreal, pick is very situational and can go literally any adc
Support - Thresh, Zyra, Morgana, Leona
My pool is really crap for top, but I despise playing top, so I don't really mind playing any of my jungles top and just get tanky really.