I main support....and i can't really carry from this position if the rest of my team is ass. But i caaaaan play someone like janna and do my best to keep these idiots from feeding as hard as they're trying to.
And i can't emphasize this enough: WARDS. wards. wards. wards. upgraded trinket is cheap af. Let me know if you need help for some good places to ward, but it's vital and it's a team effort, not just support who can only put 3 down. everyone can put a pink down, and vision goes a long, long way to helping you pick off people and know exactly where your enemy team is.
Dragon really is important, I played a game where we had over 20k more gold, more than twice their kills, but drag was 6-1 and we just couldn't keep up and eventually lost. kills are never, ever more important than objective control. ever. You can kill the enemy team all day long, but if dragon and towers aren't being taken, you'll never win unless the enemy team isn't getting them either. Seriously, dragon gives amazing buffs the more you get it, and it can be game-breaking. jungle dieing to out-smite dragon is perfectly acceptable- i would totally do it.