My suggestion is u'll fine out soon enough. Just select 5 champs at most for 2 lanes and practice them super hard in normal games. Eventually, u'll realize urself what works bc there r so many parameters and factors which not even RIOT openly reveals (as ppl go nuts trying to obtain it forgetting tw counts mostly as it is instead of solo kills or ks) but which will definitely make sense once u do well enough and earn that S. Just today, finally got my first S on Jhin which I thought was never possible for lvl 7 (2 more to go), thinking as he has range it might not count that he is always involved in fights and be able to get it, but I did even though the score wasn't anything special 7/0/10.