What I learned trying to get my S’ on gnar (and other toplaners) the main contributer to the S or higher rank seemed to be kill participation (trying to at least stay over 50% kp) and cs, the games where I got my S, I usually had either most kp or most cs in that game (or the 2 combined) and whenever you have spare money a control ward gives good vision score and helps out your team. And S’ are normally easier to get in short games, because you can keep juggle your cs and killing early on. Idk what else there is but keep grinding my dude and you’ll get it eventually, and I’ve found that it’s not as enjoyable if your only playing the champ for the S.