Here's what I found playing in low elo: Just ignore your team. Let them do whatever the hell they want, and try to finish games fast. Late game in bronze or silver is horrible, it stretches on for 40+ minutes and once I have played a game where a team threw so badly, they lost when we had an open nexus. Here's how you win games:
-Give 0 craps about lane. If you get a kill, that's great, but once you have ult, start roaming. if you play mid, roam bot or top when you see kill opportunities. Try to make plays, and don't just take kills and leave, kill the laner, and try to take a tower, low elo ppl usually insta back, but push lane instead. There is no point in staying in lane if you are not getting objectives, farming back and forth for 15 minutes is a waste of time.
-If you are top, roam down. When I play top and if I am unable to push hard enough to take tower, I just roam mid, try to make something happen, then roam bot and try again, this gives you a TON of options as you can get dragon from here. REMEMBER: never use tp to go back to lane, coming to lane to get 5 cs isn't worth it. Save TP for roaming to fights, or just walk down to lanes and save TP for when the enemy top pushes too hard.
-Don't worry about your team, and don't do anything that requires complex coordination from your team. If your team goes into a stupid fight, make sure you are there to turn it around. Don't try split pushing or farming, if your team groups, group with them to ensure that you win fights. NEVER rely on your team to do anything by themselves. So no split pushing, unless your whole team is roaming over the entire map. If your team groups, get your butt back to them ASAP, a loss of 4 kills is far worse than a turret.
-Pressure the whole map. This goes back to roaming. The trick to getting towers is to roam faster than the enemy team. you just want to be everywhere at once early on, most likely, if you roam enough, you can just get the enemy to /ff.
-Don't play ADC, unless you have a support duo, or vice versa. Botlane makes you reliant on another player which is bad.
-Save tp. Don't waste it. If it isn't urgent, walk. If it isn't safe, walk. Tp is a super strong spell people misuse because they waste it on getting around lanes to farm easier. Use it to get kills.
-don't care about farm. Your farm numbers don't matter, just try to last hit, but don't feel obligated to farm 100 cs in 10 minutes.