Okay, first off, you're not going to win every game. This is a team game, and if your entire team is just throwing away the win, then it's going to be tough to win no matter what. Sometimes you can play perfectly and your team is just too heavy. Sometimes you just gotta write off those games as a loss and move on.
That said, you can still win those games. It's ridiculously hard, and a competent enemy should crush you, but this is solo queue we're talking about, not LCS.
Step one: End laning phase as quickly as possible. If your lanes are getting wrecked in laning phase, then you need to end laning phase. That means when you gank and get kills, you take the freaking tower. Now your lane has freedom to roam and group and make non-laning plays. More importantly, you can shove their lane and tell them to roam with you so you can make 4v2 situations and help your other laners get back in the game.
Step two: Avoid the enemy team until you can win a confrontation. This is obvious, but 99% of the playerbase doesn't get it. The 6-0 Riven is probably going to shit on your lanes if they're 0-6 and behind by 100cs. They need to avoid the fed enemy team like the plague and farm elsewhere until they neutralize the lead. Tell them to farm your jungle creeps. Tell them to rotate with you to another lane for a 5v2 or 4v2 or 3v1 or whatever gank. Don't pick fights you can't win and have them sponge up enough exp and gold to hit whatever powerspike they need to turn the game around. Stall stall stall.
Step three: Increase morale with a plan. Nobody likes to get shit on. They are going to be spamming surrenders and saying gg ff@20. Now is not the time for that shit. Now is the time for leadership and inspirational bullshit.
If someone starts complaining and being negative, IT IS YOUR JOB TO STOP THAT SHIT.
"We can't win, they're too GUD."
"**NO. **Here's the plan, I'm going to come to your lane, and we're going to kill them. Then we're going to take their tower, then we're going to rotate to bot and take that tower and dragon. Then we're going to spend all of our gold, buy nice things, and rip them a few new holes. I'm coming to your lane now, get ready."
(and then commence with the hole ripping)
The plan is important. Without a plan, all they have is the losing score to focus on. Give them hope, and then make it happen.
Jungle is the hardest role in the game. You have to understand every role, every champion, control the entire map, set up for all objectives, make plays, call plays, and manage the emotions and egos of your teammates to keep the squad working together long enough to destroy the nexus in 20-50 mins. You're not going to win every game. But by no means should you ever stop trying.
My $0.02, hope it helps.
