There is a lot more to it than kills or assists.
Warding, building the right item for the right situation, countering getting countered, farming even in lanes where it's hard to farm in ( which is my biggest problem) and alot more.
I am not trying to discourage you, you should definitely aim high and go for it, just don't expect that one game means so much.
I have games that my sister fckin knocks on my door like someone got killed, makes me pause the game and all she does is look for the cell phone charger, wastes 15 seconds for no reason. Or my mom screams like ww3 has begun only so that i go downstairs and she asks me something stupid. So people can be interrupted, or carried away, sometimes my favorite show is on tv so i play like a troll while my attention in on the tv so don't hurry to jump into conclusions, challenger is a hard place to get to.
Keep trying and one day it will happen