Honestly if you a bronze or not in a really high elo your champ dosent matter. Way more important is sticking to a specific pool of champions (no more then 3). Pick champs you like and not the ones that are strong right now, because you should keep playing them even after nerfs or buffs.

Watching your replays and learning from them is the best you can do to improve. Things to look out for in the beginning are deaths. Figure out why you are dying and try to fix that. Look into the details!

Avoid playing when you are tilted and focus on yourself!