Play mid or top first off. In jungle, adc, and support you have to rely on your team. The less you have to do that the better.
Be familiar with quite a few champs so that you can counter lanes. Splitting is really strong in low elo, so if you can win lane and force the enemy to send multiple people top or mid to handle you- your team can push lanes, freefarm and get objectives. Just be sure to tell your team thats the plan and ward your self up so you can safely escape once the enemy comes.
As top laner you have the power to turn fights with tp. So tell your team to drop wards before they fight so you can come down. Try to get tp advantage on your toplaner. Which means forcing him out of lane so he has to tp back. Then you need to go back and get to lane without losing exp or using tp. Then tell your team to pick a fight- tp bot, use the advantage.
There are two super powerful things you can do to win that have nothing to do with skill.
First, don't bitch, don't flame. No matter what. It only makes your teammates play worse. Instead, tell them you'll come help, tell them when. Such as, let me push this into tower and I'll roam mid to gank. Tell them to let their lane push in so you CAN gank.
Second, help your team setup plays. If you know what you're doing, tell them what to do. Tell them things like, put a ward in the bottom bush in botlane, then let them push into you. When I ping I'm coming, engage on them hard as you can, I'll tp in and we'll kill em. Do it when you know you can win. So for instance if you're 1/4 in toplane, not the best idea, if you're 4/1 but the enemy toplaner also has tp... could still be risky. Keep track of you advantages and use them.
If you're behind in lane and your team is flaming you, fuck em, mute em all and focus on you. Don't let them or the enemy all chat distract you. Focus on what you need to do and the proper itemization that will help you win. Not just itemizing against your enemy lane, but against their team. Think about how you'll need to be useful, look at the items the enemy has, look at who is fed and build accordingly.
When you're ahead, get a deep ward on an enemy buff, then you and your jungle can go gank the enemy jungle or you can solo him, or you just know where he is so he won't surprise you. You can also waste the enemy jungles time, if you know where he is.
Lead your team by helping them. Most of losing games is decision making. Sure, some is skill for sure, but mostly its always bad decisions. Help your team make good decisions with healthy communication.
Which means, not 'Well if you would've put a ward in the brush I would've tped down.'. Instead, 'Sorry guys, we'll get it back, just put a ward in the brush for me next time you want a fight and let me know, I'll tp down and we'll blow em up, my toplaner doesn't have tp'.
Sometimes there isn't much you can do, but what you can always do is focus on you and improve you.