the best adc to carry with is your best adc. No that's not a joke. you could learn literally any adc and if you know it better than your opponent and can farm better you are already putting yourself in a good position to win.
the key to winning in bronze is learning the game and the basics of how it works. Focus on the basics of mechanics like last hitting, and how to trade/when to trade. Then learn when its a good time to take objectives, when to back, when you should abandon farming and join a team fight thats about to start etc.
Generally speaking...if as an adc you can even farm decently and team fight OK in bronze you will carry yourself out in no time flat.
I recommend maining someone. Just pick one that you are most comfortable on even if its simple and master it and only play that champion unless forced to another.
For me, that champion was Annie as a mid, and when I got stuck as a mid laner, I switched to Sivir ADC. Sivir for me was the best because she was a relatively safe laner. The spell shield allowed me to outplay any CC based supports while still having some poke, great waveclear, and mobility with ultimate. She isn't the most snowbally but in bronze you don't need that.
if you are way better than bronze, you can play anyone and would probably play someone who snowballs incredibly hard like Graves, Lucian, Twitch, Vayne.
But you don't have to be that guy to climb out of bronze. Its all about improving as a player overall and focusing on your ONE role and one champion so you can then get it without thinking. when you dont have to think about what you are doing it allows you to get better at other aspects of the game and then get better overall. that is how you climb.
As for other roles, go with one or two for each other role and only play them when forced to. dont have this huge champion pool because it will delay you getting good with any one of them. focus on your main and the others are secondary.
For example here is what I play only in ranked:
TOP=
MID=
JUNGLE=
SUPPORT=
ADC=
(if banned I go
)
but I ALWAYS go for ADC and ALWAYS pick sivir when its available no matter the matchup, no matter what, because I know those champions well and know what to do even in bad matchups. Are my picks the best? not even close. a lot of the champs I play are considered weak right now. but I know them quite well. If I go against a Riven in top lane who doesn't main riven? and I'm jax. I will probably stomp her. if I go mid and I'm against a xerath who doesn't main xerath? I will win that lane as annie because I know how to. Only because I have exclusively kept my pool low to understand these champions as best as I can.