from looking at your profile i can see that you're pretty new. unranked and ~100 normal wins is not a lot of time to learn the game, believe it or not. trust me, you will learn with time. if you want you can add me and i can help you learn some of the things you might be missing, but it's up to you
personally, i don't care about normal games, but in ranked i won a lot by literally just spamming games with champs im good at. didn't play anyone but shyvana and leona at all this season (except sivir once when my client fucked up and i couldn't trade, that was interesting and i fed a vayne 8 kills) and i was able to climb by only playing 2 champs.
as long as you're Decent at other roles and champs, as in, if you're forced out of your main role you won't feed your ass off, then you'll be fine really. focus on farming in lane and don't risk dying, because that puts you at a huge disadvantage.
something i've noticed from watching high levels of play is that most of the time, people don't die in lane, they die from ganks and teamfights. you should be playing safe in lane and not putting yourself in risky situations where you MIGHT get a kill but you also might die
also, this is preseason, and preseason sucks. everything is snowbally right now and most games end by surrendering. don't worry about preseason, hopefully everything will get fixed in the new season and it will suck less
just something to think about, i'm not an expert obviously, just been playing this game for way too fucking long. if you have any questions hmu