Why can I NEVER seem to get an S rating?
So, I've been playing as Shyvana for quite some time now, and now that I am a Mastery level 6, I need 3 Master Level 7 tokens to continue upgrading but I can never seem to get an S rating (my highest is S-) while playing, even if I do really well. For example, the most recent game I played I went 18/0/4 (K/D/A) and had 141 minion kills with a total collection of 12,268 gold and I got an A+ rating. Yes, it was a relatively short game at just under 27 minutes, but still... I think that's a pretty good ratio. Either way, can someone give me the best way to possibly get an S rating in my game? And if you could also tell me what determines any S rating and the A-F ratings that'd be helpful as well. Thanks!
Also, on the side, do the A-F ratings have any significance? Like do they give you more XP or something or are they just there to tell you how you did?