Support>Mid>Jungle>ADC>Top are how I would rank the roles in carrying at low elo.
The issue with top is that it is extremely isolated from early objectives and that winning lane might not really translate into much benefit for your team. This can be improved by picking up teleport and managing to get a double in bot, which will massively swing the game. But outside of that, you want to focus on your strongest role, support, mid, and improving your weakest role.
Support is extremely powerful for carrying in bronze, silver, and low gold (hell, even high gold really). Basically, most games are thrown in the bottom lane. Bronze players tend to give away very free kills by not warding. So being the support and having wards allows you to prevent bot from throwing.
Next, there are many champions bot that can get your lane fed and cut off their late-game power. Blitzcrank, Leona, Thresh, Annie-- all four of these champions have abilities with really high impact all game. Low elo players tend to have huge problems with hooks/grabs. Any of these champions will let you carry since people are out of position often enough for you to engage and punish. Low elo players also aren't good about knowing when to start a teamfight. Each of these champions makes it obvious when they are initiating and when it is time to fight.
Mid is the next best role to carry from. If you win lane you have huge map presence and can go anywhere. You have more money than the jungler and should be able to kill them in a 1 v 1 situation. Your basic goal is to win lane and then snowball either top or bot-- whoever looks like they will be useful if snowballed.
Jungle has decent control all over the map. The issue is that if all lanes are feeding and outmatched, you don't have a great source of danger free revenue and you won't get a lot of farm to carry with. That said, if your team is okay, you can really push them higher. The main trick to jungle is to land a counter-gank. Counterganks can really screw over the other team and cause them to go on tilt. If you ruin someone's gank and turn what they thought was a benefit into a huge loss-- it will change the course of the game.
ADC has a lot of gold, but is very reliant on the team for protection. If mid fed a squishie killer, it's going to be awful for you. However, you can likely prevent bot from feeding and ruining the game, and if you just make sure bot wins or goes better, you'll do well.
Top was already discussed. Its isolation means that even if you're 5/1, botlane could have given up 20 kills without you being able to do anything.