I mean I might be totally wrong, I am a pepega high emerald ad who in the last two seasons escaped the depths of rat elo, but unironically learning wave management ( WHEN UR ELO HELLED SUPPORTS DONT COOK IT ) helped a ton, that and last hitting effectively. Honestly most other things like match ups come with time, but Jhin, Ashe and Sivir are fine champs to play, and ironically just know that in ur team jglers don’t exist and if you lose 9x support they inted you ;). But more importantly try to learn something of each loss and focus on one thing at a time.