200+ games? em, why are you in new players forum? lol
yep, lvl10-15 is a really big gap, this is when you start to see non-weekly rotation champions, it's okay to lose in this phase, but i suggest you to read all champions description and watch Riot Champion Spotlight and understand how they basically works and what to watch out for, ex. blitz's grab, Ezreal's skillshots, Alitair's knock in the air + knock back towards turrent combo, Shen Stand United etc, so you won't be surprised in an early 1v1 or 2v2 situation. knowing your enemies is the first step towards conquering them. And in 5v5s, don't feel bad to hug towers, as long as you don't feed, it's gonna be alright, leave the rest to your hopefully pro teammates, wait them to help you gank.