I don't have a preferred champion that I like to play, because I don't like playing the same champions all of the time. I guess I would say that Veigar is my main for ranked, but that is mostly because he snowballs hard late game. I am Bronze 3. I could probably be higher, but I don't like playing ranked a lot, because it is a more serious atmosphere and I like to just do stupid things and have fun. I have a champion I like to play for every position, and generally try not to ADC. ADC's will be hated by their team if they do bad bot lane, even if it is because of a bad support, so I just stay away from bot lane when picking a position. Overall, I play to have fun and enjoy myself doing stupid things for fun. Good luck, have fun, and remember to enjoy your time on the Fields of Justice!
