League of Legends (LoL) Question: How can I avoid losing the game for my team after a bad start?

prioritize cs and not dying over looking for ways to kill your opponent if you deny enough farm eventually they let you kill them. Not dying stupidly trying to make some desperate backdoor play.

This is probably better off asked as a thread if you want to amass advice.

The most succinct way to win from behind is to know what the winning conditions of your champion are.

Take Jinx, for example. She is a strong late-game carry, who gets stronger as time goes on and scales well with items. She absolutely destroys towers with just a few items. So, given that you lose lane, what you need to do is to safely farm. Let your tower get destroyed and FREEZE the lane. The enemy should have a hard time pushing past rivers without risk of ganking from your midlane/jungle, so you should safely be able to farm. If they decide to push, your team should gank the **** out of them.

Getting dragons and other objectives will also prove helpful if you can. After that, your win condition is simply have your team protect you whilst you whittle down turrets and other objectives. As long as your team can get you close to turrets, you win. The same is basically true of teamfights.

Pantheon is different in a sense. His kit is designed to bully the lanes, regardless of whether he's is solo lane or jungle. He is not well-fitted to play from behind, but if he is put behind, he is still very good at catching people out because of his semi-global ultimate. Look for opportunities to catch people out, keep the jungle well-warded. Your best bet is also to itemize as a tanky frontliner. You need to tank the enemy damage and let your team clean up. You should stun priority targets, whether it's to peel for your carries or to dive the enemy backline. I'm by no means a Pantheon player, though.

At low levels and Elos, one consistent strategy is splitpushing, mostly because people just don't know how to deal with it. A lot of the time, you can rack up a lot of objectives just by continuously pushing one lane. To do this, you need good map awareness. As soon as you see the enemy disappear from the minimap, you need to stop pushing and recall. If you see your base threatened, then you need to go back to stall them.

Keep in mind that you are just really low leveled at the moment. Losing games is very normal and you have a long way to go to learn about the game at level 30. Don't be discouraged.

I guess everyone has a bad game from time to time and it's nothing to feel guilty for. Trying to play as safe as possible is the best advise I can offer you. As an AD carry you generally want to grab as much farm as possible but be sure to not push alone without any vision. Staying with your team often protects you from being caught and therefore you can also stay in mid lane for a while with your team, farm some minions and hope for an actual push or engage if it's a geniune situation. Defense items like Quicksilver Sash can be built earlier than usual in certain games against specific matchups but most likely you want to stick to your standard build path thus building the most cost efficient damage items. Keeping an Avarice Blade for a while in mid game can help you gaining some extra gold before finishing Statikk Shiv. It's arguably not the best option for Jinx but building SS first can help pushing lanes easier.
Warding, keeping track of your own turrets and the enemy minion waves and following your mates in case they know what they're doing are the things coming to my mind in the first place. I hope I could help you at least a bit.

Well everyone has a few bad games. Before starting a game make sure you aren't nervous. I usually see this as "losing before you start". It takes a while to get the right frame of mind so you see it as just a game because it feels pretty competitive. Also a good thing to know are matchups for the champions you like playing. I personally don't play a lot of ad carry but I know enough that you should play extremely carefully against a caitlyn because her auto attack range is disgusting and she can just poke you down and kite for days. Also you should play passively against a bot pantheon (you won't be seeing this as you ascend in level) as he has the damage to potentially, if he has good synergy with caitlyn, to kill you instantly in lane. Although you shouldn't make a habit of blaming your team, I'm level 30 and the bards over here aren't that amazing. They often stun YOU instead of the enemy. Your build looked a little weird. I generally try to steer away from runaan's. My jinx build (when I play her) is rush IE, then Shiv, bloodthirster, last whisper (boots of course somewhere in there) and banshee's veil. Late game you have a lot of power and survivability with jinx who scales EXTREMELY well into the late game. Other than that have lots of fun! As long as you see it as fun, you'll play better